Marriage licenses should be obtained before your wedding ceremony. In the state of California marriage licenses are valid for 90 days and will cost you between $35 and $100+ depending on the county requirements ($97 for Ventura County). You can get a license the day of your wedding but remember that most government offices are only open on weekdays.
To get a license, you have to fill out an application at your county court house’s Clerk Recorder’s Office. Make sure to bring your photo id, driver’s license, or passport. Some counties will also require a copy of your birth certificate. Also be prepared with your mother and father’s full names and information on previous marriages if this applies to you, such as the date your marriage ended and how it ended (death, dissolution, divorce, or nullity). Some counties may require a copy of the judgment.
County Clerks can perform civil marriage ceremonies at the County Clerk’s Office (if you’re in a hurry or on a budget) and there are requirements for those authorized to perform marriage ceremonies in California (can be a priest, minister, rabbi, judge, commissioner or assistant commissioner of a court of record, a justice, magistrate, etc.) This person is responsible for returning the original marriage license to the County Clerk or County Recorder within 10 days of the ceremony. You will not receive a copy of the license unless you pay for it and request one from the County Clerk or County Recorder.
It is good to check online to find out the specific cost and requirements for your county. They may even have an online application available.