Nap wouldn't happen to be IndiaNAPolis would it?
Anyway, you're young and right now is when you need to prepare. First advice, stick with your sports. All four years. You might want to quit but don't. I wish I had taken that same advice when I was younger.
Also, keep working for A's and B's and taking the hardest classes you can handle those in. Your GPA/class rank will rise as long as you continue to do that. (I had a 3.7 Weighted Freshman year, 4.2 now at halfway point in Junior)
Join clubs ASAP. Be a member for a year or so and get to know influential people (read: popular) and get them to support you as you run for Elected positions in those same clubs or in a student government. If your grades and EC's are up to par, you will likely be inducted into the National Honor Society at the end of Soph. year, which is a check in the box on USMA's application. Likewise with Boys' State after Junior year. Talk to your counselor about that when the time comes.
Physically, your sports should keep you in running shape. Just remember, there is no offseason for fitness. Keep running and increasing mileage. If upper body fitness is an issue and you want a pre-made plan take a look at these.
100 Pushups
50 Pullups
Obviously 50 pullups is ridiculous, but it's a plan that will AT LEAST last you until you can do a decent amount and start Recon Ron or Armstrong. (Google those if you can already do 10+ pullups)
In conclusion,
1)Stay in sports
2)Stay smart
3)Get leadership spots
4)Get and keep physically fit
You'll be getting your appointment in the mail before you know it.