How can i have a dui expunged?

I recieved my DUI when I was 20yrs old. I recieved this DUI in San Bernardino county California. I plead guilty and it was a misdomenor offense. I have no other crimal cases besides a few minor speeding tickets. I payed my fine and all that jazz. Will I be able to get my recorded expunged and how can I do this. I dont have much cash to spend. Any ideas would be appreciated