you've got to have very strong quads, hamstrings and glutes. There are a lot of exercises that you can do to strengthen those muscles, but here are the main ones:
Squats (regular or front)
Deadlifts
Romanian Deadlifts
Split Jerks
Lunges
and you have to use heavy weights. you want to make your legs STRONGER to jump higher so don't be afraid to move some heavy iron.