take it from a six-foot ex-basketball player who used to be able to dunk... jump rope. Also try to through your body into the air for hight. For control... try to get the feeling of floating. The lighter you are on your feet generally, the better for tobi (leaps.)
Build up your calf muscules. They help in jumping more than your theighs. Also, jump over a lot of things. The more you practice and longer the better you'll become.