Save up some money, I'd say at least $5,000. You're going to need at least enough money to get you through a couple of months without pay, and to set an amount aside to get you home if your plan doesn't work out.
Before you go, find a place to stay. Use craigslist to find a home already looking for a roommate. Be as discerning as you can possibly be. Make sure they are aware and OK with it being a short-term situation (potentially). Try to establish a video call with the roommate(s) before you make a final decision. Hopefully they can do it from within the apartment/house and could maybe give you a remote tour.
Give them your money.
Change your address with the post office and any non-sensitive accounts so that you might have some mail waiting for you at the new address when you arrive. This will help you prove your local residence to employers.
Line up some job interviews. Internships are good, but have a fallback plan -- apply for some restaurant/service industry jobs. Anything that pays. Unless you've got rich relatives who are going to support you, or you are sitting on a pile of inherited money, you're going to need an income. Best to accept this now. It's expensive to live in SF. Living far from family and friends can introduce unexpected expenses, not to mention just the cost of the occasional visit home. My brother lives just 180 miles north in Chicago and is in a perpetual state of brokedness. He works and has three roommates, but still has a hard time coming up with enough money to cover the travel expense and lost wages from visiting home. SF is even more expensive than Chicago.
Move to SF. Don't take more with you than you can get back on your own in a hurry.
Get an updated ID card with the new address. Change any sensitive accounts to this new address (credit cards, student loans, etc.)
If you burn through your cash to the point where all you can afford is to move back, then that's the time to move back. Don't stay any longer than that. If you can't afford to return, then you're gonna have a bad time. You will stress over being broke. You won't have money to eat. Your new roommates will resent you not paying your way and being a mooch. That is until they evict you, then you're really screwed. Leave when you can still afford it and try again later, after you've saved up even more money than you had before and have a provable, marketable skill.
Source: Someone who did it wrong.