First, please don't take our word as bible, there are many Many MANY ways of both protecting your bicycle and getting it stolen. But there are a few things to keep in mind for riding your bike around; whether it's San Francisco or the East Bay, or really any urban center anywhere.
Cables are not enough, anywhere. Period. Bolt cutters make fast work of a cable. A chain-style lock can also be used as long as it is one of the larger style links; see the images below. The 30 seconds it takes you to do so will save you the panicked moment you realize it's gone, the 5 minutes of frantically looking around and asking people what they saw, the hour of walking to the police station to report it(and the many hours there while you wait), and the money you spent on it. If it's worth even the convenience of having it, just lock it up. Ask you're LBS about which lock is better for your bike. Investing in your u-lock ensures you don't have to buy the bike again. Here's a great article from the SFBC on how to thread the u-lock through your bike, or come in and ask us!
Yea, that dark alley around the corner from a bunch of sketchy characters all sitting together is probably NOT the place you want to lock. For multiple reasons. Ladies, I don't ever want to see you lock your bike in a place like that, keep yourself safe as well as your bike.
3b. Movie theaters, yoga classes, schools, etc. are all very susceptible to theft because the thief knows you are going to be in there for a certain amount of time. Most of the time, if it's not your bike, it's the pieces of your bike that go missing. My tip; move it a block or so and park in front of a restaurant. The thief is never sure if you're sitting in the window with your latte watching carefully.
3c. Make sure what you lock to is securely in the ground/bolted down and has a top that your u-lock won't fit over. Some thieves leave just one bolt in place and wait until you leave and pull the whole bike rack up.
Seismograph did a zoom-able map that shows where most SF bike theft occurs and what time of day it was; referenced in articles by The Bold Italic and SF Examiner. Check out your frequented neighborhoods to know if you just need to move your bike one block over.
Yea, I know, I know, you have to go find a quote, and pay money every month, etc; but what you don't know? It's around $20 a month. Seriously. You get something around $10,000.00 of coverage for $20 a month. Drunk roommate left the door open and your computer got stolen? You ran into the grocery store and your bike got stolen? Jessica Saia at The Bold Italic delves into the ins and outs of SF renters insurance. All of these scenarios can get covered by your renters insurance; check this article by Nerdwallet.com for a few suggestions. Your bank or your car insurance might even give you an extra deal for making another policy with them.
Your serial number is stamped into the metal on the bottom of your bike, usually alphanumeric, under the bottom bracket(on the bottom near the center of the pedals).
Receipts will ensure you get the full value if your bike gets stolen; including that new Brooks saddle, reworked handlebar set, etc. Also, some lock companies will give you money if you have their cut lock(they need to know it was their lock that failed). Check with yours, but Kryptonite, Onguard, and Abus all have guarantees. Make sure to read them BEFORE you need them. Safebikes.org is really the only registry the SFPD check, if they check any at all. BikeEastBay.org as well as the City of Berkeley recommends registering your bike on BikeIndex.org; if it's already stolen, they have a few tips and tricks to finding it as well as Google and Facebook groups that blast the message out to those who subscribe. Don't just take our word for it; here's a link to the Sheldon Brown article on locking and Live Work Oakland's article, "How not to get your bike stolen in Oakland-or anywhere" that recommends two u-locks at all times!Despite the initial reaction of, "You should've locked it better," theft is not your fault. The only one to blame is the thief, but we'd like to help you keep your hard-earned stuff, damnit!