Quick answer: Stop safely, check for injuries and call 911 if anyone is hurt, exchange license/insurance/plate info, photograph everything, and don't admit fault. Report to your insurer promptly, and file the DMV SR-1 form within 10 days if anyone was injured or damage exceeds $1,000.
At the scene
Stop and move to a safe spot (shoulder, parking lot) with hazards on; California law requires stopping after any collision. Check everyone for injuries and call 911 if anyone is hurt or traffic is blocked. Exchange with the other driver: name, driver's license number, insurance company and policy number, and plate number — and photograph their license, insurance card, and plate rather than transcribing. Photograph everything else too: all four corners of both vehicles, close-ups of damage, the whole scene with street signs, skid marks, and debris. Get names and numbers of witnesses. Say what's factual and nothing more — do not apologize or say “I didn't see you”; fault is decided later from evidence, and scene statements get quoted back.
If police respond, get the report number. If they don't (common for minor Bay Area fender-benders), your photos and notes are the record — make them thorough.
In the following days
Notify your insurer promptly even if you don't intend to file a claim — most policies require notice, and the other driver may claim against you regardless. See a doctor if anything hurts; soft-tissue symptoms often appear a day or two later, and undocumented injuries are hard to claim. And file the California DMV's SR-1 form within 10 days if anyone was injured or killed or property damage exceeds $1,000 — mandatory regardless of fault, separate from the police report and the insurance claim, and skipping it can cost you your license. At current repair prices, almost any visible damage clears $1,000.
Before you accept any settlement
Get a repair estimate — before accepting any quick settlement for vehicle damage. Remember that in California you choose the body shop, not your insurer. Spark Collision Center in Fremont offers free estimates with no appointment, we photograph and document everything for the claim, and we'll handle the adjuster conversation from there. Keep our number, (925) 599-1137, in your glovebox — the moment after a crash is a bad time to start googling.