You're off to a good start - keep doing what you're doing and you'll have a good shot at getting in.
Admissions looks at the "whole person" deal - that is:
-Does well in academics. Straight-A's are good, but they'd rather have someone with good-if-not-quite-perfect marks in AP, Advanced or dual-enrollment classes than a 4.0 in basket-weaving. No matter what your major, you're going to be taking a lot of tough classes in humanities, math and science at Canoe U, and they want to see that you've got all-around game.
-Athletics of some kind. To my knowledge, there's no points for one sport over another (team vs. individual, contact vs. non-contact) or for being a rocks star vs just a hard worker. I was a seriously mediocre wrestler, but that was fine with Admissions. Of course, leadership positions (like team captain) and things like All-State are nice extras to have, but what they really want to see is that you're not a couch potato and that you will stick with a physically challenging environment.
-Leadership positions. You don't have to be President or Captain of everything, but showing real leadership or management of something is a plus. Shows you stick with an activity long enough to know what you're doing and help run things.
Oh, and don't bother trying to "pad your resume" by joining a bunch of activities or clubs just to have them on your application. It doesn't impress and might backfire. Admissions would rather see someone with dedication to and leadership in a few different activities than "member of" 100 things.
-Biggest of all, they want to see that you're serious about being a Naval officer. Make no mistake, the Boat School sucks a lot of the time, and it's hard work all the time. The only way you'll get through is if you no-$hit WANT to be there. Don't go in there with the attitude of "I could go anywhere, and this is just one of my options." Do your research, show the admissions dudes and your interviewers that you know what the program's about and you're ready to take it on.
Good luck! It's a tough place to be, but a great place to be from.