The answer is in, technique and practice, but also leg strength. You might be able to get a better jump if you do more squats, deadlifts, and Olympic lifts, especially the snatch, though it's pretty much the hardest compound lift around. Squats are like, the "classic" exercise for leg strength, but snatches are all explosive power, and you're pretty much jumping the weight over your head, if that makes any sense. Alot is just keeping the core straight whilst jumping, too. I don't know, dunking would be cool. I'm 5'9 and I can touch about the middle of the net. Haven't tried recently, though.