Level up easy

These are some easy ways to level up your Pokemon.

Every type:

Battle the Hoenn Gym Leaders, Tate and Liza, they have two Pokemon which will both self destruct. This becomes irrelevant once your Pokemon are near level 40.

Find a dark type pokemon, a Sableye from Route 22 will due. After that, battle the Random Trainer, Psycho, in a 2v2. Battle with Sableye and the Pokemon that you wish to train, note that the other Pokemon must be a higher level and be the one to faint Psycho's Pokemon. Psycho's psychic type Pokemon will not be able to touch Sableye, but they will only attack him. This may require some patience if your Pokemon are not very strong.

Dark Type:

Battle the Random Trainer, Psycho, in a 1v1. He will use all psychic type Pokemon and they will range from level 77-89, none of which will be able to touch a dark type. This may require some patience if your Pokemon are not very strong.