Welcome to PokéCommunity! Register now and join one of the best fan communities on the 'net to talk Pokémon and more! We are not affiliated with The Pokémon Company or Nintendo.
find a building that's next to a patch of grass. Then keep on going in the building, coming out, (spray a repel) go in the grass, walk around, and then repeat the whole process
you defeat certain pokemon (EV's are based on a pokemon's naturally high stat - i.e. zubat = 1 speed ev)
have fun =)
for more info --> https://www.psypokes.com/dex/evtraining.php?id=diamondpearl