I agree your high school might be the best place to start.
But if you are looking for some ideas, here are some basic questions:
What class year are you? This will determine what you should be doing if you are interested in being recruited for a D3 tennis team. If you decide not to go that route, you could also consider club tennis. They can be quite competitive.
Do you have a budget? Are you interested in merit aid? [Edit: looks like you are fine with full pay]
Any idea what sort of college you would like? Bio and Chem are widely available, so people with those interests could like smaller liberal arts and sciences college, medium-sized research universities, or larger research universities.
Any thoughts on campus style, setting (urban, suburban, rural, etc.), region, or so on?