Just go to court on the date the cop wrote in. There you will plead guilty and pay the fine, or if available you can go to traffic school if you haven't had another moving violation within the last 18 months.
If you plead not guilty here in CA, then a trial date will be set up and that's when the cop gets a subpoena and you fight it out in court with the cop.
If he got you on radar, chances are the judge will 99.9% of the time rule in favor of the cop. I don't know if that's a California thing or what.
If the cop paced you and gave you a ticket, here are some things you should do if you want to fight it:
When you plead not guilty and the court issues a subpoena for the cop, make sure your instructions state something to the effect of: subpoena officer's vehicle speedometer calibration certificate, subpoena officer's log for the day of the citation (this is to see what vehicle the officer was assigned to); subpoena the posted "traffic survey" report with the officer. That is usually used only for radar tickets, but if the cop doesn't bring all the stuff you requested, you may claim that your case be dropped.
Chances are that the cop may not show up in court if he sees all the stuff you are subpoenaing for a simple little infraction.
Good luck.