Like the main series Pokémon games, Pixelmon incorporates a system allowing a Pokémon to grow in strength based on the opponents it defeats. This is done with hidden values known as Effort Values (EVs) that exist for each of the six stat values. This system works identically to the one found in the Pokémon games, and so an understanding of the mechanics found there should allow you to EV train successfully within the Pixelmon mod.
All Pokémon, when defeated in battle, yield a species-specific spread and amount of EVs that is given to all Pokémon that participated in defeating the fainted opponent. These are added to a possible total of 510 EVs a single Pokémon can gain, with a limit of 255 for each stat. They are applied to the Pokemon's stats immediately, without the need to level up. EVs will gradually contribute more stat points as the Pokémon's level gets higher, up to a maximum ratio of 4 EVs to 1 stat point at level 100.
In order to train Pokémon for their maximum battling potential, players are generally seen to train for 252 EVs in two desired stats, leaving four EVs to add an extra point to a third stat. More advanced players may choose to distribute the available stat points differently, to allow for more specific capabilities in battle.
Before you begin to EV train, review the following:
Once you have ascertained the above, you are ready to go out and train.
Now that you are out in the wild, look for a Pokémon that you know yields the desired EVs. Be sure your Pokémon can defeat it. Pokémon yield the same amount of EVs regardless of level, so if you are in doubt, it may be best to hold out for a lower-level Pokémon. Once they are defeated, record the EV gain and repeat the process.
Occasionally, a Pokémon may initiate a battle with you. If this happens with a Pokémon that does not yield the desired EVs, run. Running is dependent on the active Pokémon's Speed and the opponent's Speed, so if you have a higher level Pokémon in your party, switch to them rather than attempting run off the bat. If you can't get away, it may be best to allow your Pokémon to faint. Although this reduces Happiness, it will prevent your Pokémon from gaining unwanted EVs. The easiest way to avoid random battles is by avoiding Pokémon you don't want to battle, especially those with high aggravation such as Arbok.
Once gained, EVs are permanent and cannot be lost or overwritten, so one may begin battling normally as soon as the Pokemon has gained all of its desired EVs.
There are several Held Items that help speed up EV training.
All of these items halve the speed of the holder while they are worn.