Depends on the nature of the crime, depends on whether or not you're off probation... in other words, more detail is required. I'd go see a recruiter; just because you talk to one doesn't mean you have to sign up. They're there to distribute information and help you with the enlistment process. Many of them will even drive out to your house to talk to you.
I'd suggest collecting whatever documentation you can from your local courthouse, and sitting down and having a meeting with one. Worst case scenario, he will tell you it's a no go (if you don't get the documentation together, chances are he'll tell you it's a no go because he doesn't want to deal with someone with a criminal record who isn't serious about joining).
To sum up: get your medical and criminal records ready, dress well, speak confidently (but not arrogantly), and with a little bit of luck, he'll be able to file for a waiver and push you off to MEPS.
