You can still register to vote until October 20th, and can request a form be sent to you by going to this website: Voter Registration - CA Sect. of State.
Here, you'll find a few options, but the one I used is under #2 - you can have a Voter Registration Form mailed to you. Fill out the information, and they'll print it out and send it to you. All you have to do is sign it and send it back postmarked by October 20th (you still have time!).
Plus, the Registar of Voters in Santa Ana (overseeing Orange County) will actually be open until midnight on October 20th, with DRIVE THROUGH REGISTRATION. Yeah! You can still register, tell your friends!
Also, in OC you can go to any of the early voting polls! I'll be working at the one at Chapman University from October 20th until the 28th, but it will be open on the 19th as well (I just won't be there that day). ANYONE registered to vote in Orange County can go to ANY of these polling places before November 4th to vote, making it more convenient to vote. Early voting polls will be open for these 10 days, especially handy if one doesn't believe they can vote on Election Day at their local polling place (or if you don't know where it is). You can find a list of these polling places at the official OCVote.com site, which also gives the address for the site I'll be at. Drop by the Chapman one and I'll help you check in!
You can still register to vote Absentee (now called "Vote by Mail") until October 28th, too. If you wish you can drop your Absentee/Vote by Mail ballot off at the Early Election Polling places, but just know if you've already sent in a ballot, don't vote again at a poll (no multiple ballots will be counted).
So remind your friends who have moved or who haven't registered to do so now!
(You don't need ID to vote - just verify your information when checking in at the polls. If this is the first election you are voting in, you only need proof of residence. So you can't use a lost ID or having no ID as an excuse!)