certain pokes have certain stats they are strong in, such as Raichu in speed and altaria in sp. def. say if you want to raise speed, you battle only wild zubat until you level up, and keep battling them.
try looking on bulbapedia about IV's or EV's. Or seribii.net. Both are useful resources. Last night I EV trained my lvl 45 Umbreon on Raichu, it obtained +11 speed, and my typhlosion earned +13. This was on Gale of Darkness though.