What I tell everyone here who asks what they can do to increase their chances of admission is to first look at the makeup of current classes at the academies and make sure they at least meet if not exceed those stats. For example:
No one can chance anyone for a service academy appointment due to the vagaries of the nomination process. You must have a nomination before you can be considered for admission and no one can tell you how you stack up to the competition in your particular congressional district in the year you apply.
In the meantime, you should be taking advantage of all the rigor your high school offers which means taking the highest/most rigorous courses available to you, especially in calculus, physics, and chemistry as the academies are primarily engineering schools. You should also be pursuing team sports and leadership as well as upping your physical condition to the highest level you can. West Point scores candidates based on a Whole Candidate Score (WCS=60% academics, 30% leadership, and 10% physical), so you need to be the best you can be in each of those silos. Once your candidate profile is open, you will be assigned a Field Force Representative (FFR) who will guide you through this process and will have some insight into how competitive you are in your district. This is the primary person you need to stay in contact with as your FFR can answer any questions you have. This resource will tell you to do your best academically, up your physical fitness game, and pursue leadership opportunities. You will want to show quality over quantity, stay focused, and put your best application forward. Ultimately, that’s all you or any candidate can do. If you want to listen to and participate in the conversation of candidates and parents who are a little further along this path, lurk on serviceacademyforums.com which is the official website for those applying to service academies. This site is the place to research previous discussions such as what is the female experience is like (LOTS of threads on that one), how to prepare for interviews, how to deal with DoDMERB issues, etc. That forum is moderated by current and former military officers and staff who are more than willing to share their firsthand knowledge.