Here are four phone numbers that I recommend all San Franciscans keep programmed in their cell phone. I use the numbers on a fairly regular basis (except the emergency one, thankfully).

Emergency, 911: 415-553-8090
Use the number for emergencies.

Non-emergency Police Dispatch: 415-553-0123
Use this number when you see people acting suspiciously and would like a patrol car to check things out.

Department of Parking and Traffic (DPT): 415-553-1943
Use this number when you come across vehicles parked on sidewalks or other places where they don’t belong. I use this number fairly regularly.

311 City Customer Service: 415-701-2311
This number is sort of a catch all that the public can call to access information about government services.