Many Admission Directors are looking favorably at those perspective students who have been involved in their community. If you are involved now you will most likely be involved later in college campus activities. In addition, many good application essays have come from volunteer experiences. Athletically, play, play, play, go to camp and play some more. The more you play the better you will most likely become at your sport.
Camps are the big summer activity that can be fun and rewarding.
Ideally, attending a camp on a college campus or where college coaches are coaching would be the best option. Camps are a chance for athletes to gain exposure to college coaches. Many college coaches find their recruits at camps. The other place to be observed by college coaches is at the state, regional, and national level playing against the best in your sport. Many college coaches have limited budgets, thus they attend major tournaments where they can evaluate a number of athletes at one stop.