I am just a candidate and I may be way off base here, but from everything I have heard and everyone I have talked to it isn't just a numbers game. Yes, your scores and grades matter but it's about being a well rounded individual. No other school I have applied to takes into account intangibles as much as the academies do. Leadership, athletics, service to others, they all contribute to your character and development. I don't think there is a formula for what to do to get accepted, I think you need to develop every aspect of your life to the best of your ability and let the chips fall. Good luck.
I don't believe that is true. USNA uses something called WCS and WCS is a number that is calculated based on all of the things you have done. For example, you will get more points on your WCS if you increase your ACT score by 5 points or for becoming the captain of a sports team or for maxing out every event on your CFA. I have read that the 150 candidates with the highest WCS on the NWL must be admitted. So I think a large part of the admissions process really is just numbers. If you have a very high WCS your chances of getting in are much better than someone that has a very low WCS.
Also, I'm not sure if this is true for USNA, but I have read that for USMA there is a point value assigned to activities. If you do the activity you get X points on your WCS for it, if you don't do the activity you don't get X points on your WCS. It doesn't appear to be all that subjective to me.