Strength to weight ratio
If you do not have strong legs, you probably will not be able to jump high. Lower body strength is vital in producing a good vertical leap. The squat to 90 degrees has shown to be the most accurate figure in determining an athletes ability to jump. The ratio between an athletes maximum deep squat and their body weight has been shown to be an excellent indicator of an athlete's vertical jump.

Flexibilty
If you are not flexible, you are only limiting your ability to jump. If you muscles cannot move in a ideal range of motion, your power output is going to be limited and jumping technique will be distorted. It is absolutely vital to make a commitment to stretching if you plan on jumping higher.

Central Nervous System
Coordination and quickness and efficiency of movement are very important in jumping higher. The faster you can apply the strength you have, the more power you generate. Greater power output=Greater vertical jump

To be Continued