Three right turns.
There are many places in San Francisco where you just can't make a left turn. There are enough of them, that when you say "San Francisco left turn", people know what you mean.
Sure, "No left turn" signs occur in other places, but usually you can just turn left on the next block. In SF, you sometimes have block after block where no left turn is allowed. If you're downtown on Market looking for a chance to make a left turn, you'll practically end up in The Castro before you're allowed. (unless you're a taxi driver, they're allowed... I don't understand that)
So, here is how to make a left turn in San Francisco:
Get into the left turn lane, and signal left turn. Slow down to make your turn. Now slam on the brakes and swear like a sailor when you notice the little "No left turn" sign you missed before. Proceed straight through the (green) light and quickly get into the right lane. Make three right turns, and you'll end up back on track! (as long as your third right doesn't hit one of those right turn only streets; don't get me started)
Do not, I repeat, do not stay in the left lane, telling yourself you might be able to get left at the next light. Before you know it, you'll end up in Daly City. I'm exaggerating, but don't say I didn't warn you.
Contrast with How to make a left turn in LA and New Jersey left | 
