If you have a College Degree (or will get one soon), complete it first. Than go in through OCS. Officer Candidate School.
I took this to mean Marine OCS, ie. comment below. But the above line may have been meant in general.
Looked into that route a couple yrs ago. In the end I realized the corps wasn't for me at that point in my life. Also I managed to get only 6 pull ups after 2.5 months of training my upper body and barely passed the PT requirement. For Marine OCS it is really high I believe somewhere around 215-240 on the Marine PT test with average OCS candiate scoring much higher. I strongly recommend reading "A Bullet Away" an excellent book about OCS and a Recon Marine officers personal story. I can hook you up with some more reads the recruiter I talked to back then recommended. I am still pissed though my then girlfriend didn;t let me go up in the Hornet, ie. initial discussion happened at Purdue's airport and I am a private pilot although my vision would have disqualified me from aviation anyway.