Start your day off on the water at Fisherman's Wharf. From here you can see the resting sea lions, get a sour dough bread bowl full of SF's famous clam chowder, and play some old-timey arcade games at Musée Mécanique (as seen in Princess Diaries). Then walk down to Ghirardelli square for an ice-cream-sunday.
Walk the world famous Golden Gate Bridge or have a nice picnic below it at Christie Fields. For another great view of the bridge, take a walk down the Lands End trail, starting at The Sutro Baths. Be sure to keep an eye out for migratory whales!
Check out San Fransisco's China Town, starting at the famous Dragon Gates. There are some really great restaurants and shops in the area. Did you know the fortune cookie was actually invented in San Francisco? Finish your visit at the Golden Gate Fortune Cookie Factory and then pick up a cable car to go to your next stop.