Sign up for the Civil Air Patrol (CAP). Gives a taste of the military in uniform & gauges interest. Can help answer: "Why military" question during application.
Need to show good grades (straight As preferred), community service & junior varsity or varsity in sports.
Summer internship or job viewed positively. 10th summer onwards is important.
Another option is to apply for summer military run programs to bolster your application.
Apply for the Academy (Navy, Air force or Army) requesting a nomination through the local senator's office. Highly competitive. 8% acceptance. Equivalent to Ivy League & has a host of courses & degrees, ranging from STEM, medicine to philosophy. Attend college in uniform. Fully paid & get stipend. Need to serve for 5 years. Can drop out in 1st year if not interested with no penalty. Credits can transfer. No buy-out option beyond 1 year. Usually opens in April of Junior year. Needs good SAT.
Apply for ROTC (Reserve Officers’ Training Corps) scholarship. Used to be easier but hard nowadays. Doesn't pay as much as academy. Pays for college (affiliated with ROTC). Can drop out before 2 years if not interested with no penalty & credits can transfer. Usually need to apply by September after Junior year. Can apply for both Academy & ROTC. Requires 4 years service after graduation. Having ROTC scholarship can boost resume.
If married while in service, Military tries to keep married people together. Govt gives preference to federal jobs for spouse. If on active duty, a federal job is made full remote job to spouse.
Usually 'enlisted' people get deployed. Academy & ROTC service is an Officer level training in charge of planning & strategy. Chance of getting deployed to active combat is relatively low. US military loses more people to suicide & self-harm than external combat.
Post service, will be considered a veteran & can help in civil job applications, since they could have gained experience managing up to 100 soldiers.
Some people do pilot training in the academy, serve, then join commercial airlines after the service period is over.