EXPUNGEMENT

Ask your attorney to file a petition and order for expungement, Judicial Counsel Form CR-180. You can do this yourself, actually, although your attorney will probably have a better shot at succeeding. Here's the link:
http://www.courtinfo.ca.gov/forms/fillable/cr180.pdf.
There's a $60 fee, payable to the clerk of the applicable court. If you do it yourself, be sure to serve the prosecutor, and to add a certificate of service to the form you file with the court.

Be sure to check with an attorney in your jurisdiction on expungements because most will expunge if you have only one offense. In other words, if you have prior convictions you are not eligiblle for an expungement. So before you pay a filing fee be sure you qualify.