The best way to increase your vert jump is to do plyometrics. There are many diff. exercises and some of them you shouldn't do until you have a good base. You can do a search on the net or if you want check out this site for descriptions on exerecises.

http://www.radix.net/~madsox/CATS/exercises.html

By the way, I'm 6'0 and after a summer of ply. I dunked with ease.