Go to the USAFA website and read all the application criteria.
Unless you are the child of a Medal of Honor winner, you want to ensure your combined score is as high as possible. Ideally, you should be good enough at a sport to be a candidate for a college scholarship. Your HS grade point average should be 3.7 to 4.0. You should be involved in several activities that indicate leadership potential--sports team captain, cheerleader, religous group/youth leadership, HS clubs, HS student government, work/intern experience.
You should have the best recommendations lined up you can get. One should be from your religious activities. A few should be from your high school--principles and teachers. Maybe you "ran" a prom or homecoming, etc for your high school. One or more should be from coaches. If you worked/interned, one should be from that business. These people should hold the highest positions. They should recommend you based on your character, honesty, ability, community service and leadership ability.
The military academys regard leadership as having an "x" factor. Something unique about the individual that provides their success in leadership. It's helpful if your recommendations mention the unique part of you.
If you score highly enough, you will be evaluated by a Senator or Representative. Some use just your records. Some have a committee do an interview. If you go to the interview, consider it a job interview. Try to "win" each senator staff member over as you go through the interview. Each interview team will have: a woman, a minority, a military officer, an athlete, a staff member. You want to show that you have staying power. If they nominate you, you will stay and graduate.