How?!?

Hey, I was wondering how people get there plants to be so bushy, like have more than just one central branch. Mine are like tall and all but hardly filled in with leaves and stuff and to be honest looks quite pussy. I was thinking of pruning them (cutting off the top growing place) so that it would give time for the branchs to come up on the sides. But i dont want to force the plant into a male or herm. Its about erm 2 months now and the plants are about a foot and a half big. They were in pots and were root bound for a little but now there inthe ground and they get sunlight all day. But still looking pussy besides my one she looks pritty nice. Please gimme feed back on how to make her yeild more.