A few thoughts ...
1. Don't allow "taking the class" to trump learning the subject matter. Math, writing, chem, physics are the most critical areas. These are not hurdles to get over but rather tracks to run on. They'll not go away once you've gotten the "A" in the class or the 34 ACT math score.
2. Really take time to prepare for your SATs AND ACT. Take them both early, get a feeling, and take them as often as you're willing and able. Ask for the prep books for Xmas, rham-a-don, Yom Kippur, or festivus ...and take the practice exams.
3. Alert your MOC to your interest in junior year. Same w/ BGO. Ask your counselor or other locals in the know who the latter is. You can do these earlier, but not necessary. Find out who your BGO is and how to contact him/her. Follow their guidance if/when offered, but remember, they are not, in many cases either necessarily engged and interactive in this process. There is enormous variability. And don't be fearful to communicate appropriately with your admissions staff at USNA. Remember ...your parents pay his/her salary and they are there to work for you. And when you do communicate? YOU do it, not mom or dad.
4. Swim, run, do push-ups regularly and often and put up a pull-up bar and work on it every day.
5. Get and read, cover to cover and more, the book "The Naval Academy Candidate Book." Used to be Smallwood, now a newer edition by Sue Ross. Scads of cheap ones available on Amazon(I wonder why? ;-)duh...). Learn the process, the timetable for both application and nomination processes, make a list.
6. Stay healthy ...physcially, legally, morally. And don't have any corrective eye surgery and do have your wisdom teeth extracted. Zero 'toos!!!
7. Pray for great math and English teachers your junior year and bust hump for both. And when time comes (and before) let them know that their significant, detailed, positive endorsement letters will be necessary to boost your candidacy. These 2 are specific and important.
8. 01 Feb 2011 ...submit your application for NASS (summer seminar). This is not critical nor essential for appointment, but can be helpful for many reasons. And should you go? Be 100% prepared to do your absolute max on the physical fitness test which will be given day #2 there. Running, push-ups, crunches, pull-ups, basketball throw. Practice and work at them all.
9. Explore your history to see if you can check one of the diversity/minority boxes. Seriously. This can be transforming in your application.
10. Pray for the USNA god's mercy and grace through this complex, arduous, and challenging process. And if you're not a person of faith, you're on your own.
11. Recognize, especially if you're as good and able as you appear to be, the 2 most challenging steps in this are:
A. Application and nomination processes. It's FAR more statistically challenging to be 3Qed, nominated and appointed than it is to graduate and be commissioned. In fact, given the first 3 steps? The latter 2 are virtual locks with one caveat. See item 11(B). btw, also statistically tougher getting a slot in NASS than USNA, so don't sweat that much, ifn you fail to get a summer slot.
B. Be committed to knowing what an appointment and 4 years at the Academy is and is not. It's NOT a "free education" nor college-in-uniform experience. It is preparation to lead and potentially put your life on the line for the well being of your nation and its citizens. It's a minimal commitment of up to 8 years, and ideally longer. The whole intent is to ID and prepare USN and USMC career officers. Most fall short of that, but that is the exclusive purpose.
Congrats and kudos for asking the right question at the right time. It's not too soon, believe it.