Pokémon/Competitive battling/Effort Values (EVs)

First, please note that EVs only appear in the Third Generation. EVs are hidden values that can increase your Pokémon's stats. You can obtain EVs for every stat (HP, Attack, Defense, Special Attack, Special Defense, and Speed), with a maximum of 255 EVs for one single stat and 510 EVs total for all of the stats combined. For every 4 EVs of one stat, your Pokémon will gain 1 point to that stat. For example, if you gained 4 Attack EVs, then your Pokémon will gain 1 point in its Attack stat. It sounds great, right? How, then, do you obtain EVs to raise your Pokémon's stats?

Vitamins
Vitamins are HP Up, Protein, Iron, Calcium, Zinc, and Carbos. Each vitamin will give you 10 EVs of HP, Attack, Defense, Special Attack, Special Defense, and Speed, respectively. However, you can only use 10 Vitamins of each kind, with a total of 51 Vitamins can be used.

KO'ing a Pokémon
Believe it or not, fainting a Pokémon will gives you from 1 to 3 EVs of one stat, or the EVs could be split into 2 stats but the maximum EVs you can get total from one Pokémon is 3. For example, Aron gives +1 Defense EVs. If you fight a lot of Arons, then your Pokémon's Defense will raise faster than your other stats, since for every four Arons you KO, you get +1 to your Defense stat. Since the maximum EVs you can gain for one stat is 255, the EVs that you can use is actually 252, since 252 can be divided by 4. This is important if you go through a process of "EVs training," meaning that you will only battle certain Pokémon to get the EVs you want. Giving a Pokémon 255 EVs of one stat is a waste of 3 EVs, since instead of 255 + 255 = 510, you can split up 252 + 252 + 6 = 510, and the 6 EVs (actually 4) will be used for another stat. Two EVs will be left unusued no matter what. Even if you're not so keen on undergoing complete EVs training, you can train in an area where there are many Pokémon that gives the EVs that you want. If you battle online, you will be able to set your Pokémon's EVs. This is very important because you can give up to 63 points to a single stat using EVs. I will now provide a list of which Pokémon receives what EVs.

Note: Although it seems better to try to look for Pokémon that gives +2 or +3 EVs, these Pokémon are probably very rare and are not populous, so it is actually faster to find an area with many Pokémon with +1 EVs and KO them instead. Pokémon      EVs received   other EVs received

a) HP EVs

Caterpie        1 Point      None Nidoran (F)     1 Point      None Nidorina        2 Points     None Nidoqueen       3 Points     None Clefairy        2 Points     None Clafable        3 Points     None Jigglypuff      2 Points     None Wigglytuff      3 Points     None Slowpoke        1 Point      None Grimer          1 Point      None Muk             1 Point      1 Point (Attack) Lickitung       2 Points     None Chansey         2 Points     None Kangaskhan      2 Points     None Lapras          2 Points     None Ditto           1 Point      None Vaporeon        2 Points     None Snorlax         2 Points     None Mew             3 Points     None Hoothoot        1 Point      None Noctowl         2 Points     None Chinchou        1 Point      None Lanturn         2 Points     None Igglybuff       1 Point      None Marill          2 Points     None Azumarill       3 Points     None Wooper          1 Point      None Quagsire        2 Points     None Piloswine       1 Point      1 Point (Attack) Phanpy          1 Point      None Blissey         2 Points     None Entei           1 Point      2 Points (Attack) Celebi          3 Points     None Wurmple         1 Point      None Shroomish       1 Point      None Slakoth         1 Point      None Slaking         3 Points     None Shedinja        2 Points     None Whismur         1 Point      None Loudred         2 Points     None Exploud         3 Points     None Makuhita        1 Point      None Hariyama        2 Points     None Azurill         1 Point      None Delcatty        1 Point      1 Point (Speed) Gulpin          1 Point      None Swalot          2 Points     None Wailmer         1 Point      None Wailord         2 Points     None Barboach        1 Point      None Whiscash        2 Points     None Castform        1 Point      None Tropius         2 Points     None Wynaut          1 Point      None Snorunt         1 Point      None Glalie          2 Points     None Spheal          1 Point      None Sealeo          2 Points     None Walrein         3 Points     None Relicanth       1 Point      1 Point (Defense) Jirachi         3 Points     None

b) Attack EVs

Beedrill        2 Points     1 Point (Sp. Defense) Ekans           1 Point      None Arbok           2 Points     None Nidoran (M)     1 Point      None Nidorino        2 Points     None Nidoking        3 Points     None Paras           1 Point      None Parasect        2 Points     1 Point (Defense) Mankey          1 Point      None Primape         2 Points     None Growlithe       1 Point      None Arcanine        2 Points     None Machop          1 Point      None Machoke         2 Points     None Machamp         3 Points     None Bellsprout      1 Point      None Weepinbell      2 Points     None Victreebel      3 Points     None Muk             1 Point      1 Point (HP) Krabby          1 Point      None Kingler         2 Points     None Hitmonlee       2 Points     None Rhydon          2 Points     None Goldeen         1 Point      None Seaking         2 Points     None Scyther         1 Point      None Pinsir          2 Points     None Tauros          1 Point      1 Point (Speed) Gyarados        2 Points     None Flareon         2 Points     None Dratini         1 Point      None Dragonair       2 Points     None Dragonite       3 Points     None Totodile        1 Point      None Croconaw        1 Point      1 Point (Defense) Feraligatr      2 Points     1 Point (Defense) Sentret         1 Point      None Spinarak        1 Point      None Ariados         2 Points     None Unown           1 Point      1 Point (Sp. Attack) Snubull         1 Point      None Granbull        2 Points     None Qwilfish        1 Point      None Scizor          2 Points     None Heracross       2 Points     None Teddiursa       1 Point      None Ursaring        2 Points     None Swinub          1 Point      None Piloswine       1 Point      1 Point (HP) Octillery       1 Point      1 Point (Sp. Attack) Kingdra         1 Point      1 Point (Sp. Attack & Sp. Defense) Donphan         1 Point      1 Point (Defense) Stantler        1 Point      None Tyrogue         1 Point      None Entei           2 Points     1 Point (HP) Larvitar        1 Point      None Pupitar         2 Points     None Tyranitar       3 Points     None Combusken       1 Point      1 Point (Sp. Attack) Blaziken        3 Points     None Mudkip          1 Point      None Marshtomp       2 Points     None Swampert        3 Points     None Poochyena       1 Point      None Mightyena       2 Points     None Nuzleaf         2 Points     None Shiftry         3 Points     None Breloom         2 Points     None Sableye         1 Point      1 Point (Defense) Mawile          1 Point      1 Point (Defense) Carvanha        1 Point      None Sharpedo        2 Points     None Camerupt        1 Point      1 Point (Sp. Attack Trapinch         1 Point      None Vibrava          1 Point      1 Point (Speed) Flygon           1 Point      2 Points (Speed) Cacturne         1 Point      1 Point (Sp. Attack) Zangoose        2 Points     None Seviper          1 Point      1 Point (Sp. Attack) Solrock         2 Points     None Corpish          1 Point      None Crawdaunt        2 Points     None Anorith          1 Point      None Armaldo          2 Points     None Shuppet          1 Point      None Banette          2 Points     None Absol            2 Points     None Huntail          1 Point      1 Point (Defense) Bagon            1 Point      None Salamence        3 Points     None Groudon          3 Points     None Rayquaza         2 Points     1 Point (Sp. Attack) Deoxys          1 Point      1 Point (Sp. Attack & Speed)

c) Defense EVs

Squirtle        1 Point      None Wartortle       1 Point      1 Point (Sp. Defense) Metapod         2 Points     None Kakuna          2 Points     None Sandshrew       1 Point      None Sandslash       2 Points     None Parasect        1 Point      2 Points (Attack) Poliwrath       3 Points     None Geodude         1 Point      None Graveler        2 Points     None Golem           3 Points     None Slowbro         2 Points     None Shellder        1 Point      None Cloyster        2 Points     None Onix            1 Point      None Exeggcute       1 Point      None Cubone          1 Point      None Marowak         2 Points     None Koffing         1 Point      None Weezing         2 Points     None Rhyhorn         1 Point      None Tangela         1 Point      None Seadra          1 Point      1 Point (Sp. Attack) Omanyte         1 Point      None Omastar         2 Points     None Kabuto          1 Point      None Kabutops        2 Points     None Bayleef         1 Point      1 Point (Sp. Defense) Meganium        1 Point      2 Points (Sp. Defense) Croconaw        1 Point      1 Point (Attack) Feraligatr      1 Point      2 Points (Attack) Sudowoodo       2 Points     None Pineco          1 Point      None Forretress      2 Points     None Gligar          1 Point      None Steelix         2 Points     None Shuckle         1 Point      1 Point (Sp. Defense) Magcargo        2 Points     None Corsola         1 Point      1 Point (Sp. Defense) Skarmory        2 Points     None Donphan         1 Point      1 Point (Attack) Miltank         2 Points     None Suicune         1 Point      2 Points (Sp. Defense) Silcoon         2 Points     None Cascoon         2 Points     None Seedot          1 Point      None Pelipper        2 Points     None Nincada         1 Point      None Nosepass        1 Point      None Sableye         1 Point      1 Point (Attack) Mawile          1 Point      1 Point (Attack) Aron            1 Point      None Lairon          2 Points     None Aggron          3 Points     None Torkoal         2 Points     None Duskull         1 Point      1 Point (Sp. Defense) Dusclops        1 Point      2 Points (Sp. Defense) Clamperl        1 Point      None Huntail         1 Point      1 Point (Attack) Relicanth       1 Point      1 Point (HP) Shelgon         2 Points     None Beldum          1 Point      None Metang          2 Points     None Metagross       3 Points     None Regirock        3 Points     None Registeel       2 Points     1 Point (Sp. Defense)

d) Special Attack EVs

Bulbasaur       1 Point      None Ivysaur         1 Point      1 Point (Sp. Defense) Venusaur        2 Points     1 Point (Sp. Defense) Charmeleon      1 Point      1 Point (Speed) Charizard       3 Points     None Butterfree      2 Points     1 Point (Sp. Defense) Oddish          1 Point      None Gloom           2 Points     None Vileplum        3 Points     None Venomoth        1 Point      1 Point (Speed) Psyduck         1 Point      None Golduck         2 Points     None Abra            1 Point      None Kadabra         2 Points     None Alakazam        3 Points     None Magnemite       1 Point      None Magneton        2 Points     None Gastly          1 Point      None Hunter          2 Points     None Gengar          3 Points     None Exeggutor       2 Points     None Horsea          1 Point      None Seadra          1 Point      1 Point (Defense) Jynx            2 Points     None Magmar          2 Points     None Porygon         1 Point      None Zapdos          3 Points     None Moltres         3 Points     None Mewtwo          3 Points     None Quilava         1 Point      None Typhlosion      3 Points     None Natu            1 Point      None Xatu            1 Point      1 Point (Speed) Mareep          1 Point      None Flaaffy         2 Points     None Ampharos        3 Points     None Sunkern         1 Point      None Sunflora        2 Points     None Espeon          2 Points     None Misdreavus      1 Point      1 Point (Sp. Defense) Unown           1 Point      1 Point (Attack) Girafarig       2 Points     None Slugma          1 Point      None Remoraid        1 Point      None Octillery       1 Point      1 Point (Attack) Houndour        1 Point      None Houndoom        2 Points     None Kingdra         1 Point      1 Point (Attack & Sp. Defense) Porygon2        2 Points     None Smoochum        1 Point      None Raikou          1 Point      2 Points (Speed) Torchic         1 Point      None Combusken       1 Point      1 Point (Attack) Beautifly       3 Points     None Ralts           1 Point      None Kirlia          2 Points     None Gardevoir       3 Points     None Masquerain      1 Point      1 Point (Sp. Defense) Roselia         1 Point      None Numel           1 Point      None Camerupt        1 Point      1 Point (Attack) Spinda          1 Point      None Cacnea          1 Point      None Cacturne        1 Point      1 Point (Attack) Seviper         1 Point      1 Point (Attack) Lunatone        2 Points     None Chimecho        1 Point      1 Point (Sp. Defense) Gorebyss        2 Points     None Latios          3 Points     None Kyogre          3 Points     None Rayquaza        1 Point      2 Points (Attack) Deoxys          1 Point      1 Point (Attack & Speed)

e) Special Defense EVs

Ivysaur         1 Point      1 Point (Sp. Attack) Venusaur        1 Point      2 Points (Sp. Attack) Wartortle       1 Point      1 Point (Defense) Blastoise       3 Points     None Butterfree      1 Point      2 Points (Sp. Attack) Beedrill        1 Point      2 Points (Attack) Ninetales       1 Point      1 Point (Speed) Venonat         1 Point      None Tentacool       1 Point      None Tentacruel      1 Point      None Drowzee         1 Point      None Hypno           2 Points     None Hitmonchan      2 Points     None Mr. Mime        2 Points     None Eevee           1 Point      None Articuno        3 Points     None Chikorita       1 Point      None Bayleef         1 Point      1 Point (Defense) Meganium        2 Points     1 Point (Defense) Ledyba          1 Point      None Ledian          2 Points     None Cleffa          1 Point      None Togepi          1 Point      None Togetic         2 Points     None Bellossom       3 Points     None Politoed        3 Points     None Hoppip          1 Point      None Umbreon         2 Points     None Slowking        3 Points     None Misdreavus      1 Point      1 Point (Sp. Attack) Shuckle         1 Point      1 Point (Defense) Corsola         1 Point      1 Point (Defense) Mantine         2 Points     None Kingdra         1 Point      1 Point (Attack & Sp. Attack) Hitmontop       2 Points     None Suicune         2 Points     1 Point (Defense) Lugia           3 Points     None Ho-oh           3 Points     None Dustox          3 Points     None Lotad           1 Point      None Lombre          1 Point      None Ludicolo        3 Points     None Masquerain      1 Point      1 Point (Sp. Attack) Spoink          1 Point      None Grumpig         2 Points     None Swablu          1 Point      None Altaria         2 Points     None Baltoy          1 Point      None Claydol         1 Point      None Lileep          1 Point      None Cradily         2 Points     None Milotic         2 Points     None Kecleon         1 Point      None Duskull         1 Point      1 Point (Defense) Dusclops        2 Points     1 Point (Defense) Chimecho        1 Point      1 Point (Sp. Attack) Regice          3 Points     None Registeel       1 Point      2 Points (Defense) Latias          3 Points     None

f) Speed EVs

Charmander      1 Point      None Charmeleon      1 Point      1 Point (Sp. Attack) Weedle          1 Point      None Pidgey          1 Point      None Pidgeotto       2 Points     None Pidgeot         3 Points     None Rattata         1 Point      None Raticate        2 Points     None Spearow         1 Point      None Fearow          2 Points     None Pikachu         2 Points     None Raichu          3 Points     None Vulpix          1 Point      None Ninetales       1 Point      1 Point (Sp. Defense) Zubat           1 Point      None Goldbat         2 Points     None Venomoth        1 Point      1 Point (Sp. Attack) Diglett         1 Point      None Dugtrio         2 Points     None Meowth          1 Point      None Persian         2 Points     None Poliwag         1 Point      None Poliwhirl       2 Points     None Ponyta          1 Point      None Rapidash        2 Points     None Voltorb         1 Point      None Electrode       2 Points     None Staryu          1 Point      None Starmie         2 Points     None Electabuzz      2 Points     None Tauros          1 Point      1 Point (Attack) Magikarp        1 Point      None Jolteon         2 Points     None Aerodactyl      2 Points     None Cyndaquil       1 Point      None Quilava         1 Point      None Furret          2 Points     None Crobat          3 Points     None Pichu           1 Point      None Xatu            1 Point      1 Point (Sp. Attack) Skiploom        2 Points     None Jumpluff        3 Points     None Aipom           1 Point      None Yanma           2 Points     None Murkrow         1 Point      None Sneasel         1 Point      None Delibird        1 Point      None Smeargle        1 Point      None Elekid          1 Point      None Magby           1 Point      None Raikou          2 Points     1 Point (Sp. Attack) Treecko         1 Point      None Grovyle         2 Points     None Sceptile        3 Points     None Zigzagoon       1 Point      None Linoone         2 Points     None Taillow         1 Point      None Swellow         2 Points     None Wingull         1 Point      None Surskit         1 Point      None Vigoroth        2 Points     None Ninjask         2 Points     None Skitty          1 Point      None Delcatty        1 Point      1 Point (HP) Meditite        1 Point      None Medicham        2 Points     None Electrike       1 Point      None Manectric       2 Points     None Plusle          1 Point      None Minun           1 Point      None Volbeat         1 Point      None Illumise        1 Point      None Vibrava         1 Point      1 Point (Attack) Flygon          2 Points     1 Point (Attack) Feebas          1 Point      None Luvdisc         1 Point      None Deoxys          1 Point      1 Point (Attack & Sp. Attack)

3) Ways to speed up EVs Training

Yes there are, and they're not really hard to get (well some of them). The items or events below affect EVs Training in some way.

a) Macho Brace

The game does not tell you what the Macho Brace is for, besides the fact that it halves the wearer's Speed. That can't be all that it does, since it will make the Macho Brace useless. In fact, the wearer will gain double whatever EVs it gets. Fainting a Taillow while wearing a Macho Brace will give you 2 Speed EVs (Taillow originally gives 1 Speed EV). If your Pokémon is at a high level and won't be affected by the huge Speed decrease, then please use this great item!

b) EXP. SHARE

As you all know, the wearer of EXP. SHARE gets half of the experience while not in battle. Also, the wearer will get EVs, not half, but full. If your Jolteon faints a Taillow and your Zigzagoon (that was never in battle) has EXP. SHARE attached, then both Jolteon and Taillow gains 1 EV. This is a good way to train up weak Pokémon both experience-wise and EV-wise.

c) The PokéRUS

If you haven't heard of this before, the PokéRUS doubles the EVs received, just like the Macho Brace. This is good, but the PokéRUS is random whether or not it will infect one of your Pokémon. If you're lucky enough to have it, then it will infect your whole party. The PokéRUS will go away, so if you want to keep it so that it could infect new Pokémon, then put one infected Pokémon in a box, since the PokéRUS doesn't go away if the infected Pokémon is in a box. When the want to infect a new Pokémon, withdraw the infected Pokémon and when it infects your party, put it in a box again. Note that a Pokémon that has been infected by the PokéRUS will not get PokéRUS again, since its Memory T Cells will ensure that.