The first thing they have to do is improve their flexibility, for a couple of reasons. They need to be flexible to undertake the kind of exercises they need to be able to jump higher. They also just need to be able to increase their flexibility, because in the short sprints you take when you try to dunk a basketball, if you can imagine yourself running up to try to dunk on the rim, the higher you can bring your knees in a sprint, just like a sprinter running the hundred meters, the greater force you’ll be able to exert on the ground, especially with your leaping step.
My son asked me to get book to help improve his jump and was thrilled with the terrific tips it gave him. According to him, this book covers all the important basics and is a must-read for anyone looking to increase their athletic performance. The exercises are described in a clear, easy to follow manner...and now that I've read it as well I'm happy to say, I understand more of what my son is always going on about! ;)

A vital part of basketball training is improving your vertical leap. As an athlete, you should be incorporating exercises into your basketball drills and fitness training that focus on increasing muscle strength and leg speed. Simply put, you won’t turn into Vince Carter or Andre Iguodala overnight, but learning how to work the appropriate muscles on a daily basis will go a far way towards improving your overall vertical.

Overall, 309 patients (18.4%) had an arrhythmia; the most common type of arrhythmia was atrial fibrillation, which occurred in 266 patients (86.1%). More patients had an arrhythmia, especially atrial fibrillation, in the dopamine group than in the norepinephrine group (Table 3). The study drug was discontinued in 65 patients owing to severe arrhythmias — 52 patients (6.1%) in the dopamine group and 13 patients (1.6%) in the norepinephrine group (P<0.001). These patients were included in the intention-to-treat analysis. There were no significant differences between the groups in the incidences of other adverse events.
I gave myself ten weeks to dunk again. It wasn’t going to be easy: I figured I’d need to add five or six inches to my vertical in order to dunk a regulation basketball. I was in half-decent shape, and at six-foot-three, I had height on my side. But I had a few things other than age working against me—namely feet that had flattened over the years to canoe paddles, and an ankle injury I’d never properly rehabbed.
I am 5''11 with a 43 inch vertical I am a freshman and I play on the varsity team as a point gaurd I can do 360''s and now a 540 I want to tell you how I can dunk all I did was watch Vince carter and watch the motion he does and I did the same motion and I never thought I could dunk until the beginning year of 8th grade now I am a freshman posterizing 11 and 12th graders.
An important component of maximizing height in a vertical jump is attributed to the use of counter-movements of the legs and arm swings prior to take off, as both of these actions have been shown to significantly increase the body’s center of mass rise. The counter-movement of the legs, a quick bend of the knees which lowers the center of mass prior to springing upwards, has been shown to improve jump height by 12% compared to jumping without the counter-movement. This is attributed to the stretch shortening cycle of the leg muscles enabling the muscles to create more contractile energy. Furthermore, jump height can be increased another 10% by executing arm swings during the take off phase of the jump compared to if no arm swings are utilized. This involves lowering the arms distally and posteriorly during the leg counter-movements, and powerfully thrusting the arms up and over the head as the leg extension phase begins. As the arms complete the swinging movement they pull up on the lower body causing the lower musculature to contract more rapidly, hence aiding in greater jump height.[5] Despite these increases due to technical adjustments, it appears as if optimizing both the force producing and elastic properties of the musculotendinous system in the lower limbs is largely determined by genetics and partially mutable through resistance exercise training.[6][7]