The easiest way to train your pokemon is to press start,pick the pokemon you want to train, press summary and check how much EXP it needs to get to the next level, then put that pokemon in the Day-Care(Which is in Solaceon Town if you did'nt already know) and take that many steps. each step counts as 1 EXP point.

NOTE:You can do this with two pokemon at a time and you m ight sometimes lose a move.