This book is great. I was a little worried because I am a girl an wasn't sure if these excerises were gonna be too hard or effective. But Jack Cascio shows great exercises and explains the science behind vertical jump. He explain the exercises step by step and give you a website where to go if you need a visual. Very informative and great info. Will definitely help you increase you certain will you help you gain knowledge about it also.
Start on a lower hoop and practice on that, just to get the feel of dunking. Jump height is one thing, but you would be surprised at the number of people that find it hard just to slam the ball into the basket, even if they are high enough. Make sure the hoop is high enough for you to only touch the rim. Different jumping styles and distances from the basket can change your vertical drastically and could be the difference between a rim-block and a slam. Keep progressing and eventually you will see results. Good luck!

Whether the result of a 180° spin or body angle at takeoff, the double clutch is generally performed with the player's back toward the rim. While this orientation is rather conducive to the double clutch motion, Spud Webb was known to perform the dunk while facing the basket. Additionally, Kenny "Sky" Walker, Tracy McGrady—in the 1989 and 2000 NBA Contests, respectively—and others, have performed 360° variation of the double clutch (McGrady completed a lob self-pass before the dunk). Circa 2007, independent slam dunker T-Dub performed the double clutch with a 540° spin which he concluded by hanging on the rim.[9]
Turn on the windmill. As you approach, bring the ball into your abdomen and back, extending your arm behind your body and up in a circular fashion, like a windmill spinning. At the apex of your jump, bring your arm all the way around to throw it down like a boss. Dominique Wilkins, the Dunkmaster General of the 90s, used to blow crowds away with this spectacular dunk.

Then, in terms of exercises, you really need to get your whole body stronger. You need to improve your core, and obviously you need to improve your legs. So someone who is interested in jumping higher will find themselves doing a lot of squats. And I would suggest that if someone just started this, they could do a lot of squat exercises without even going to the gym or even bearing weight. You know, get up in their office cubicle and do ten squats. Three sets of ten reps of squats is a good workout.
A second, more efficient and correct method is to use an infrared laser placed at ground level. When an athlete jumps and breaks the plane of the laser with his/her hand, the height at which this occurs is measured. Devices based on United States Patent 5031903, "A vertical jump testing device comprising a plurality of vertically arranged measuring elements each pivotally mounted..." are also common. These devices are used at the highest levels of collegiate and professional performance testing. They are composed of several (roughly 70) 14-inch prongs placed 0.5 inches apart vertically. An athlete will then leap vertically (no running start or step) and make contact with the retractable prongs to mark their leaping ability. This device is used each year at the NFL scouting combine.