What people have said on here already..
- Shopping at downtown(near Union Square)
- Visit Legion of Honor or if you're a science nerd, go to the Academy of Science or Exploratorium
- Golden Gate Park
- Tourists stuff, go to Fisherman's Wharf, Sutro Tower, North Beach
- Go to SBC Park and catch a Giants game.

-And yes, stay away from Hooters in SF. They're ugly. My friend was sooo pissed he didn't even leave a tip because ours looked hurt.
- If you want to see some nice jailbait, go to Serramonte which about 15-20 minutes from SF depending where you are.
-Stay away from the Tenderloin, Hunter's Point, and Sunnydale