roll your hips under, and laces face behind you when you are at the top of the jump.
conditioning so you can jump higher, snap your legs up higher and snap them back down in time.
Stretching- sit in a straddle with your feet up on something and have someone push you down
Sit in a straddle and lift your right leg off the floor a couple time, then repeat on yuor left leg, and then do both! Then try to hold it there! I hope you understand what I'm saying.. haha. It helps me a lot!