You’re not a true Californian, at least according to the law, until you get a local driver’s license and blue-on-white license plates from the Department of Motor Vehicles. If you’re moving from another state, they will ask you to complete a written test of 36 questions, and you are allowed to miss 6 on the first try (the number drops to 3 afterwards) and still be eligible for driver’s license. The information on what to bring to the DMV for driver’s license exam is on their Web site as well.
If you’re located somewhere in the Silicon Valley, the chances are that you will be required to visit Santa Clara DMV, right on Flora Vista off El Camino Real. I would strongly suggest getting in their online appointment system, as on the day of my visit there were 70 or 80 people in line with no appointments and 4-5 persons in line with appointments, and as they proceeded through the tickets (2 non-appointees, 1 appointee seemed to be the pattern of the day), it bumps you up (the appointment itself, of course, meaning nothing - no one there greets you personally and tells you they’ve been waiting for you).
If you’re registering your car in California and have brought it in from another state, there are two things you need to do before you come inside the DMV building to your appointment. Get a smog inspection, which can be done on a gas station or mechanic’s shop, which usually would portray a red checkmark, and signs “Smog inspection”. You will need this form to get a license plate. I had to choose between the gas stations located close to the DMV, and so had to pay $50 for the service, but if you’re smart, you’d do it beforehand on any gas station that does it for $25-30. Then, don’t immediately park the car in the lot of Santa Clara DMV. Instead, head around the building to the verification line, where they would inspect the car for something rather (the note they handed me assured the recipient the car had 4 wheels and used gas).
Bring a checkbook, as they won’t accept credit cards, and there are no ATMs in sight. Bring a pen, since they always mysteriously disappear from the desks where you’re pointed to for the exam. Study some sample tests for driver’s license. Overall, a visit to DMV with appointment ready and all paperwork (smog inspection and verification) in place should not take more than an hour. Also, visit this New to California? page that DMV put up. The cars brought into the state should be registered with the DMV within 20 days. The driver’s license must be obtained within 10 days after starting a job here.