Having a sick vertical proves your athleticism and looks cool. Get those mad ups:
1) Body-weight Squats
They make you stronger and because they mimic the crouch position of the jump, they're great practice. Graduate to jump squats.
2) Calf Raise
Shaq did them every night before bed when he was in college, and his vertical leap increased by 8 inches. Aim for a big number-- 400, say-- and break it up into sets.
3) Jump Rope
Jumping rope hits the same muscles you use in your vertical leap. Incorporate it into your training two to three days a week, continually increasing session length.