If you didn't do community service or pay a fine, it was most likely dismissed.

You should obtain an FBI background check.

Send $18 and your fingerprints to the FBI records divison. It usually takes about a months or so for the results.
Check the website for details.

http://www.fbi.gov/hq/cjisd/fprequest.htm

You should also do a statewide or county search to see if anything comes up. This can be done at your state or county court records dept.