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?
1) 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.
2) Fainting 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 faint, 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 recieves 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 faint 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.