Personally I love walking around SF, It's a vibrant city. You can really get a feel for the city by walking it. So I'd start with walking around Union Square, and just west of Union Square where you'll find a lot of galleries. Post, Mason, Sutter Taylor streets etc.
While there, (Union Sq.) check out the St. France, it was the old Hotel Utah's sister Hotel. Check out the lobby of the Sir Francis Drake Hotel. (Powell St.) Then walk down Bush St. to the gates of China Town and walk through and explore CT until you get to North Beach and Washington Sq. Then wander around and make your way to Telegraph Hill and Coit Tower. From there you can wander down to Fisherman's Wharf. If you want to see Alcatraz, you're in that general area where the tours start.
From Fisherman's Warf you can walk West to Hyde St and catch a cable car to Lombard St and walk the Crookedest Street” From there, You can either head over to the Marina District check out the Palace of Fine Arts and go down to the bay for closer views of the Golden Gate Bridge. Or wander around Russian Hill and Nob Hill.
You'll find restaurants everywhere, a lot of little Thai places, Chinese, Italian in No Beach, Sea food on the wharf etc.
Other options, Museum of Fine Arts. Haight Ashbury/Golden Gate Park. Although if you go to Haight, you'll have to pick me up some hippy beads
I like the Japanese Tea Garden in the Golden Gate Park. A great little spot is China Beach
http://www.californiabeaches.com/beach/china-beach/ There's Golden Gate National Recreation Area, and Presidio. Walk across the Golden Gate.
If you have a car and want to see some sights out of the city, there's Muir Woods, 12 miles north of the Golden Gate
Bridgehttp://www.visitmuirwoods.com/ From there, it's a great little drive to Stinson Beach.