Before you start

A valid visa or other admission category, and work authorisation from DHS for anything paid
An electronic I-94 record from the CBP website
A California address, evidenced for the licensing application
A booked DMV appointment — the real constraint

Step-by-step

1
Download your I-94 in the first few days
It records your admission class and 'admit until' date, and it is what employers, the DMV and the Social Security Administration will ask for. Retrieved electronically from the CBP website, free.
OnlineWho: YouWeek 1
2
Book the DMV appointment before you unpack
California's deadlines are short and Bay Area DMV appointments run weeks out. Booking is the first thing to do with a California address, ahead of gathering documents, because the appointment date is what everything else has to fit around.
OnlineWho: YouDay 1–3
3
Wait about ten days, then apply for a Social Security number
The SSA verifies your status against DHS systems that lag entry by one to two weeks. File Form SS-5 in person with your passport, visa and I-94. There is no fee.
In personWho: YouFrom ~day 10Free
4
If you cannot get an SSN, file for an ITIN
IRS Form W-7 produces an Individual Taxpayer Identification Number for tax filing, accepted by many banks and landlords. It grants no right to work.
OnlineWho: You
5
Decide between a REAL ID and an AB 60 licence
California issues a REAL ID-compliant licence to people who can document lawful presence, and an AB 60 licence to residents who cannot — the latter is valid for driving and insurance and is explicitly marked as not acceptable for federal identification. The document sets differ. Know which you are applying for before the appointment.
OnlineWho: You
6
Understand what happens to your status if the job ends
In a valley where most employment-based status is sponsored, this is the question that matters most and the one people research last. Grace periods after employment ends are short and category-specific, and a layoff clock runs from the last day of employment rather than from when you find out. Establish your own category's rules while things are calm.
OnlineWho: You
7
Keep a copy of every immigration document in two places
The I-94, visa page, approval notices and SSN card are asked for repeatedly across the first year — by employers, banks, landlords, the DMV and Covered California. Scan them once and keep the set reachable from a phone.
OnlineWho: You

Documents you’ll need

Passport with valid visa
I-94 admission record from the CBP website
Form SS-5 for a Social Security number, or IRS Form W-7 for an ITIN
Two proofs of a California residential address, as specified by the DMV
Certified English translations of any non-English documents
Social Security number, or an ineligibility letter, depending on the licence class

Things most newcomers don’t know

California's new-resident clock is the shortest in this app.

Detroit, Baltimore and San Antonio give 30, 60 and 90 days respectively. California's DMV guidance gives 20 days to register a vehicle you brought with you, and the licence obligation for a driving resident is commonly cited as 10. Against Bay Area appointment queues that is genuinely tight, and the fix is to book on day one rather than to plan around the deadline.

Source: California DMV — new to California

California licenses residents regardless of immigration status — on a marked credential.

Under AB 60 California issues a driver licence to an otherwise-qualified resident who cannot document lawful presence, marked as not acceptable for federal purposes. It lets people drive and insure a car legally, which in this metro is the difference between working and not. It is not a REAL ID and it changes nobody's immigration status. Texas, by contrast, will not issue one at all.

Source: California DMV

Sponsored status makes a layoff an immigration event, not just a job event.

Silicon Valley's employment is unusually cyclical and unusually sponsored. Grace periods after employment ends are short and vary by category, and they run from the last day worked. People who research this after the email arrives are already spending the clock. Know your category's rules, and know what a transfer requires, before you need either.

Source: USCIS

The visa sticker's expiry is not your permission to stay.

A visa authorises travel to a port of entry; the officer there decides how long you may remain and records it on the I-94. People routinely plan around the wrong date and discover the error at renewal.

Source: US Customs and Border Protection — I-94 record

Common mistakes to avoid

Treating California's window like Texas's 90 days and missing it entirely.
Not booking a DMV appointment until the documents are ready.
Visiting a Social Security office in the first week, before DHS records have synced.
Treating an AB 60 licence as a REAL ID at an airport.
Discovering your post-employment grace period on the day you need it.

Some of this may be out of date. Spotted something inaccurate? Help us keep it right for the next newcomer.