First off, if you refer to a Marine as a soldier again, you may end up getting head-shotted from 500 yards away. Just sayin'...
Second off, you can have no Felony convictions, no domestic violence incidents. Be honest about anything that's happened - nothing gets you the boot faster than an integrity violation.
Third off, you must be within height/weight standards, or at least the shipping-out standards, which are SLIGHTLY more lax. Your local recruiter will have the most up-to-date charts.
Fourth, pass the Initial Strength Test: At least 2 pull-ups, 45 crunches in 2 minutes, and a 1.5-mile run in... I believe 15 minutes. Possibly 14.
Fifth, you MUST be a High School graduate. GED doesn't get it, I don't believe.
There are other requirements, ASVAB and medical, but I can't recall them at this time.
The most important thing is to be honest, as I said. Your recruiter can work with a LOT of things, and get waivers for a whole bunch of stuff. If you show enough determination, a recruiter will move heaven and earth trying to get you in. But you have to show them that you want it bad enough. My brother's going through this process right now, fighting for a medical and education waiver (he was home-schooled, which is a whole other kettle of fish.)
Advice? Get in shape, if you aren't already. Push-ups like you've never done them before, and practice holding a push-up at various extensions: trust me, you'll need it on my Island. Running and walking are required, of course, but upper-body strength is often overlooked. Also, if you haven't taken the ASVAB recently, you'll have to take it again. Go to your local Barnes and Nobles (or a reasonable facsimile thereof) and get a Barrons guide to the ASVAB. Practice practice practice!
I wish you the best of luck in your endeavor!