I highjumped and pole vaulted in high school.
We used to do jumpsquats, power cleans, deadlifts, squats, leg presses, and hang cleans. I stayed away from the clean & jerk because my shoulders were never strong enough to keep up with my legs in high school.
Jump squats are the easiest out of the rest. Simply grab a pair of dumbells. Stand in one place, lower yourself as if you were going to squat the weight, and then explode and try to jump as high as you can. Do 12-20 reps per set and you'll be dunking in no time.
Power cleas worked great too. If you've never done it before, don't only get your technique from advice on forums and videos. Make sure you do those, deadlifts, and squats with a spotter who has personally performed those movements before and knows them well enough to explain and spot. Power clean can really mess up your back if you don't do it properly, not to mention if you overload the weight without a spotter and get it to your chest you could end up falling backwards and that will be embarassing and dangerous if you don't have a spotter present.