Lots of things can help, but you're not very specific, how much do you weight at 6'6"?
Diet is very important, most kids at this age need muscle mass/strength, and conditioning.
Did you pitch last year? How much? Most arms need an "active rest" (6 weeks if possible) period so that the muscles can heal and grow. We've used martial arts for stretching and concentration enhancement...(And just havin fun). Work with a mirror and slo-mo to visualize and perfect mechanics.
Many colleges put on end-of-year clinics attempting to look at talent coming up, so they can get scouting opportunities more focused.
Rent or borrow or buy all the stuff you can on pitching and study the art. (MLB stuff is great and a whole world of other stuff).
I guess to sum up my advice, don't put yourself in a box, look for a variety of ways in which to build ALL of your baseball skills, remember the lesson of Maddox.... He studies every hitter in the league, thus he sacrifices his time in a profitable way.