There are scholarships based on academic merit, sports talent, and financial need. In all cases, you will need to have excellent grades, and it helps if you have demonstrated your interest in your future career through extracurricular activities.
That said, it is early for you to be focusing on one particular area, so I encourage you to do your best in all your courses, especially those in science and math. You need that background to get the most out of opportunities that come your way.
I encourage you to google for volunteer positions within your community both to get experience and demonstrate your interest.