A lot of great advise. Justbaseball's advice about an instructor is great. My son's team at an early age had the head pitching scout for the Jays. It was the foundation of good mechanics. It cost $25 dollars a lesson.
TRHit's short and to the point is excellent on the e-mail. Insert a couple of action shots so that when the coach opens the e-mail it shows him what you look like. Good mechanics If you are a position player show him you know how to set up fielding a ball, swing a bat etc. An experienced coach will know what he is looking at.
We went to a college showcase at 15 and he had lots of compliments but did not go to another one until he was ready to go to college. His summer teams were very organized and had worked out right through the fall and winter in a large s***r dome. Pro scouts there instructing until they left for spring training. We also had minor league players working out as well and instructing.