It does not matter what you want to do - just do it.
Look into the branches that interest you and make your choice from there. If you want to enlist in the Army, than damn it- do it!
For some more information, talk to the recruiters but word of warning; DO NOT SIGN ANYTHING! Also BE CAREFUL as to what they may tell you. A lot of them get caught up with trying to meet quotas and will more or less 'bend' the facts to entice you to join.
I am Air Force myself. I am going to hit my 3 year mark this upcoming December. The lifestyle is ridiculous to be honest, compared to what I heard about the other branches. Just like Drake says - you are going to get shit. Period.
Last year when I was in Iraq, half the deployment we would get looks from all the Army troops and even the civilian contract workers. Why? Because we are Airforce. Its more jealousy because they treat us better (lodging, gear, etc)
But. All in all, it's not that bad a gig to be honest with you.
I myself don't like a few aspects of the AF, but thats' the same about any job. I have grown and become such a better person since I have been in and honestly I think it would do anyone good to see this side of things.
Score high on your ASVAB and when you get a choice of jobs, ensure you get something you really want to do. Sadly, I had a contract saying I was to do a job but it got mixed in so that 'voided' my contract.
Should I been a smarter Airmen at the time and not afraid of the TIs, I would of just said I want out since I wasn't getting the job I had on paper- got thrown in this on. Not a bad gig, but it be hard to see myself doing it for 20+ years.
One more note - look into the job openings. There are some that are giving bonuses, and some that are ridiculous to get into because they are going civilian contracted. If you need to know anything else, IM, Email, or post on here and I be glad to help get you anymore help or feedback.