How are your grades, now and in high school? If they're high, then I'd suggest you look into one of the federal service academies. My second choice would be ROTC, so you'll be in the branch of your choice as an officer.
If you decide to enlist, then make sure to know what you want and how to get it. If you want to be an accountant/doctor/lawyer/engineer or anything else, than enlisting in the infantry or letting the Army decide your job for you may not end as well as you think. You'll also be a different man by the time you're able to take advantage of the free education, and may not have the same drive you do now, much less a direction to go in.
What I did, is chose something and stuck with it, even though I hated it at first. Just get something on a piece of paper that begins with B.S. (or whatever) and THEN figure out what you want. IMO, unless you're a soldier/sailor/airmen/etc at heart, then going in with out a plan is a terrible plan.