http://www.yelp.com/list/one-perfect-day-in-san-francisco-san-francisco
http://www.everytrail.com/guide/one-perfect-day-in-san-francisco
It's gonna be a little hard w/o a car as here's my list of must sees:
* GG Bridge
* Coit Tower
* If you have a car, follow the "49 mile scenic drive"
http://en.wikipedia.org/wiki/49-Mile_Scenic_Drive
* For lunch have Sushi in japan town (do NOT eat in China town, rip off and bad food)
* The Grand Hyatt has a great view from the upstairs restaurant, for other great views: go to the Piano bar of the Mariott downtown
One of my favorite things to do when friends are visiting:
WALK from your hotel to Fisherman's wharf (take Coit Tower as an orientation landmark, take the elevator up to Coit Tower and then you know the direction to Fisherman's wharf) and then take the Powell/Hyde cable car back from Fisherman's wharf all the way to the end to the Powell/Mission station
just a few ideas...