I love just walking around San Francisco. The city is beautiful and has a unique atmosphere.
If you like indian/pakistani food one of my favorite restaurants is the Shalimar at 532 Jones Street. It looks really gritty, but the food is excellent, especially for the price. Try the saag or the chicken tikka massala.
I like the walk up to the Coit Tower, fun and a good view.
and my favorite thing to do in SF is visit the Musee Mecanique at Pier 45 Shed A at the end of Taylor Street, Fisherman's Wharf. As far as I remember there's no entrance fee, just bring around $5 cash to use on the machines there, it's a lot of fun!