Let me see if I can summarize a post I put up a few years ago:
1. While a senior - apply to any and all service academies of interest. In addition, if looking toward DoD service, apply ROTC programs and schools with ROTC programs. If declined by the academies but accepted by ROTC, you're on your path toward an officer's commission.
2. If the academy is the top goal and you're declined, try to get feedback on why you were declined. Also, if you don't think you're ready to take on a university level work (low ACT/SAT, for example), consider a two-year college or a prep program.
3. You can apply to an academy while attending your local community college. If so, enroll in the highest level math you place in, take courses in composition and lab based science, and be active in the college community. Retake the SAT/ACT!
4. If you choose a prep school, be aware that they fall into two categories. The first group is like NWP. They have excellent subject tutors, physical fitness instruction, and study skills instruction. They do not award college credit, but those skills go a long way to success in a collegiate environment.
5. The second group is the Military Junior Colleges. Each school awards associate's degrees so all the courses earn transferable college credit. In addition, you get exposed to a cadet lifestyle. Students also can participate in many college extracurriculars. Classes usually have a very low student/teacher ratio.
6. Often people ask "What are the self-prep appointment percentage?" That's an understandable question, but often hard to answer. A school can have a very high appointment rate by being very exclusive on who they let in. Also, students often change their goals once they get into a prep school. A better question may be, "What program will best address my weaknesses, and which one will I be most comfortable with?"
7. Finally, what is the plan B, C, D if academy admission is not in the cards. ROTC is a great path to a commission, and all services have an officer candidate path for students who already have earned their college degree.
Reach out to the admissions programs for each of the schools you're interested in. That's the best place to start the search.