Overview including links to Enlisted and Officer Candidate School (OCS).Enlist in the Marines: Enlisted Marines make up the majority of the Marine Corps and include ranks from private to sergeant major of the Marine Corps. You must be between 17 and 29 years old to enlist. You will need to receive your high school diploma before beginning recruit training; however, you can talk to a recruiter or sign your enlistment contract before graduating high school.Marine Corps Reserve: Marine Corps reservists train domestically until needed, then deploy with the rest of the Corps.U.S. Naval Academy: Every day, as the undergraduate college of the naval service, the united States Naval Academy strives to accomplish its mission to develop midshipmen "morally, mentally, and physically." The goal is a broad based education to qualify you for practically any career field in the Navy or Marine Corps.ROTC: The Navy Reserve Officer Training Corps program is designed to educate and train qualified young men and women for service as commissioned officers in the Navy's unrestricted line, the Navy Nurse Corps and the Marine Corps. Upon graduation, midshipmen are commissioned as officers.