There are so many things to do in San Francisco that a list of highlights would not do it justice! The typical highlights seem to be Union Square, Fisherman's Wharf, Alcatraz, riding the cable cars, Lombard Street, and Castro. But don't forget to stop at Twin Peaks and wander into some of the lesser-known areas of the city.
It becomes hard to pack everything you want to do into a short space of time—it is definitely worth it to spend a week or so wandering around and hitting up the "tourist" spots. I definitely enjoyed Fisherman's Wharf, because of the fantastic views as opposed to the kitschy shopping.
Quick Tips:
Try to get out of the city for at least one day of your trip. Nearby, you can find Muir Woods, Sausalito, Napa Valley, and San Jose. If you are unable to access a car, it is easy to find a tour group or other means of transportation to get to any of these popular spots.
A word of warning, though: sometimes renting a car for half a day is much cheaper and more practical than taking a tour bus. That way, you can have all the time you want to spend at each destination, and are not packed in like sardines with a million other visitors.
Best Way To Get Around:
There is no problem with finding your way around San Francisco. Between
MUNI,
BART, the cable cars, and taxis, we were never more than short walk from any destination.
Of course, you can always hoof it anywhere, too. The hills may seem steep, but they afford fabulous views! There are also several place to rent bicycles for longer trips.