Or you can do what I did and sign every piece of paper the AG Sergeant throws at you because you want to be in the military so badly you don't care what branch.
Luckily for me the Sergeant I deal with is a very good and responsible soldier, and didn't take advantage of my naivety and waited until I had calmed down and gotten serious before we started making any definite plans. But from the stories I hear from my friends who have enlisted, this is the exception rather than the rule, so like the others have said, hold out for what you want, and make sure it really is what you want.
I know it's a lot different now, but in Vietnam, my Dad (who was USAF) was in a room full of draftees and recruits and this man in civvies walks in and asks, "Who here wants to be in the Navy?"
Since the Navy was supposed to be the safest duty, half the room stands up and this man takes down their names and then says, "Welcome to the Naval Infantry, boys!" and walks out, having gotten twenty something new Marine volunteers.