Pokémon isn't just about defeating the Elite Four and beating the game—it's also about raising your chosen Pokémon into a powerful fighting force. Whether it's for your own personal satisfaction or to fight your friends, you'll want your Pokémon to be the best they can be. To do that, you'll need to start planning early.
Go for the stats[edit]
Any two Treeckos will learn the same exact skills at the same levels, but they may have significantly different strengths. Start a game, pick your Starter, check out his stats, and then restart and pick the same Pokémon again. Odds are that at least one or two of his stats will be a bit higher or lower than they were before. So sometimes it pays to catch a wide variety of the same Pokémon, since some will be faster, some will simply be weaker in all categories. If you're trying to raise a champion, make sure you're starting with champion material.
What the stats mean[edit]
HP (Hit Points)[edit]
This is the amount of damage your Pokémon can take before it faints. Obviously, the more the better, but don't overestimate the importance of HP. Mudkip has more HP than any other Pokémon, but with a low Defense stat, many Pokémon can still knock it out in a few shots.
Attack[edit]
This stat affects the amount of damage your Pokémon deal when they use physical moves, and since Generation 4, this has no more links with the type of the move. On the other hand, you have Special Moves, which is influenced by the Special Attack. Physical moves are marked by 
in the sumary of your Pokémon. You also could give a look in the Move list. Attack is linked with Defense.
Defense[edit]
This is usually more important than HP. Nosepass may not have a lot of health, but with a very high Defense score, most regular attacks will barely scratch its shell. However, a high Defense won't protect it from his weaknesses. No amount of Defense will save Nosepass from a Water attack. Defense is linked with Attack.
Special Attack[edit]
As said earlier, the Special Attack is not linked with type, so nothing is systematic. Special moves are marked by 
in the sumary of your Pokémon. You also could give a look in the Move list. Special Attack is linked with Special Defense.
Special Defense[edit]
This stat will define the resistance of your Pokémon to Special Moves, and is linked with Special Attack.
Speed[edit]
Speed is more important than you might think. Pokémon like Manectric have maybe not a terrible Defense, but with their lightning Speed ensuring they always go first, they can K.O. most foes before they even get a chance to fight back.
Get 'em while they're young[edit]
When you're catching a Pokémon you plan to use in battle, catch it as low a level as possible. Without the supervision of a trainer, wild Pokémon gain fewer stat points as they level up and may choose moves you don't want. So a level 20 Pikachu that you raised from level 5 will be much stronger than a level 20 Pikachu in the wild. Wild Pokémon may also have lost useful skills as they grow--a wild Silcoon only knows how to use Harden, but one you raised from a Wurmple will also remember how to use Tackle and String Shot!
When to Evolve[edit]
Remember that you can always prevent a Pokémon from evolving by hitting 
during the evolution screen. However, when a Pokémon is traded or exposed to a Evolutionary Stone, you cannot cancel the evolution. The reason you would want to do this is so that your Pokémon can learn skills earlier, or even skills his evolutions won't learn. For example, a Treecko will learn Giga Drain at level 21, while his evolutions won't learn it. However, evolving gets you an immediate stat boost. It is generally in your best interest to evolve a Pokémon that evolves by trading or levelling up immediately.
Pokémon who evolve via Evolutionary Stones should never be evolved until they've learned all the moves you want on them, although their evolved forms will usually learn one strong move their previous form didn't, if they learn any at all. Pokémon that evolve through trading learn the same skills at the same pace they would have if you didn't trade them, so evolve them immediately. Also, because they are traded, they gain experience a lot faster than normal, However, if you trade them away and then trade back, so that you end up with the Pokémon you originally had, you will not get the bonus. There is a lot of ways to make a Pokémon evolve, each one has it's one way, so you may want to check when exactly is the best time to make your Pokémon evolve.
Picking the right skills[edit]
Pokémon can naturally learn up to 12 skills, and with TMs and HMs, some can learn nearly 50! The only problem is that they can only know four at once... And when they forget one, it's gone forever, although you'll find somewhere in the game a man, who will be able to learn an old attack to your Pokémon again. But it costs a Heart Scale... So plan carefully which skills you want your Pokémon to have. Check the Move list for detailed descriptions of each skill, so you don't accidentally cripple your Pokémon by replacing a good skill with something bad. You also have a description while deciding which move should be forget the leave the place for the new one. A few pointers:
- Always have at least two techniques that are capable of dealing damage. The ability to lower your opponent's stats doesn't mean much when you don't have the firepower to knock them out afterwards.
- Carefully check the amount of PP each skill has. No matter how powerful the attacks are, a Pokémon with two attacks that have only five PP each is a Pokémon who will be totally spent after four or five fights. For example, let's say you have a Sceptile that can learn Leaf Storme or X-Scissor. Leaf Storme's power makes it sound more appealing, but Leaf Storme's low accuracy and PP make X-Scissor a good alternative as well.
- Stay away from novelty skills like Whirlwind or Teleport. Ending a wild Pokémon battle whenever you want is nice, but it's not worth wasting a valuable skill set.
Using TMs and HMs[edit]
In addition to the skills they learn as they gain levels, each Pokémon (save for a few like Magikarp) can learn additional skills from the TMs and HMs you find as you play the game. With the exception of a few that can be purchased in the Lilycove Department Store, there exists only one copy of each TM in the game, but good news: since fifth Generation, TMs, like HMs already before, can be teach as much as wanted. So no worries as before.
HMs are different in many ways. One HM can teach its skill to as many Pokémon as you want, but the catch is that those Pokémon can never forget it. A skill taught with an HM is a skill for life, even though, again, a man you'll meet late in the game will eventually help your Pokémon to forget it, because it's necessary when trading Pokémon between Generation. This isn't so bad when they're good HM's; even late in the game, Strength is a strong Normal-type attack, and Surf is one of the best Water attacks in the game (these moves are also necessary to progress in the game). Unfortunately Fly, Flash and Cut are all but useless later on (Although Fly is your best option for something like Pidgeot that gets no good Flying-type moves), so don't give them to Pokémon you're planning to use for the long run.
Making the perfect team[edit]
The more diverse your team is, the more likely it'll win against trainers specializing in a certain type. And even again trainers with diversified team, you'll be more polyvalent, and you'll be able to improvise something when facing a uncomfortable situation. There is no "perfect team", since everybody has is own play-style, but you can read everything in Competitive battling.
The right type at the right time[edit]
Perhaps each Pokémon's most important attribute is their type. As mentioned before, each Pokémon gets one or two types, like Electric, Psychic, Fighting, Normal, etc. Each type means three things:
- That Pokémon gets a 50% bonus when using a damage-dealing skill that matches one of his types (even for Normal skills)
- That Pokémon is vulnerable to certain attack types (for example, Fire-type Pokémon will take double damage from Water-type attacks).
- That Pokémon is protected from certain attack types (for example, Flying-type Pokémon cannot be damaged by Ground-type attacks, and will take only 1/2 damage from Bug and Grass attacks).
Remember that your Water-type Pokémon only has an advantage against Fire-type opponents if it's using Water-type attacks. Many Pokémon have types that they never learn any attack for (although they can learn type attacks with TMs). It's important to remember that types hurt your Pokémon as well as help.
As you play, you'll learn which types are good against which other types. Pokémon is like a big game of Rock-Paper-Scissors, but with fifteen different types instead of three.