When I graduated from high school, I enrolled into a Math course at a local college for the summer so that I would get exposure to college curriculum and transfer credits. In hindsight, I would have taken a Math and possibly an elective like psychology or sociology to get it out of the way. Doing this freed up room for major courses and I didn't have to spend an extra semester or year in school. It actually placed me a semester ahead and my last semester I only took 12 hrs so it gave me a chance to go on interviews, etc.
If you can in high school, take upper level Sciences and Math courses such as Statistics, Calculus, Anatomy & Physiology, Physics or even Chemistry. This will give you exposure to courses that you will have to take in College. During both my undergraduate and graduate matriculations, I always took the fast track by taken the max amount of courses I could take (undergrad-17-18 hrs and grad-9-12 hrs). I took some courses in summer school mini-sessions and also always had an internship/summer program for my CV. This exposes you to high rigor and sets you up for graduate school. I wish you the best of luck. I know that you will do well. :-)