Blimey, Upper Class! A few years back I used to go to SF about once every 6 weeks on business, but only got to go Upper Class when they upgraded me from Premium Economy - which was quite often.
If you've got the time to go sightseeing in the area, do the things that others suggest. Frank was probably talking about Yosemite (must've made a lifelong impression eh Frank
), But if you only have time to go a little bit north head out over the Golden Gate bridge, and maybe call in at Sausalito for a coffee on your way to Sonoma for a spot of wine tasting. If you go South, Santa Cruz is OK if you like Blackpool, but Monterey is cool (you can say hello to Laguna Seca on the way there as well) as is the 17 mile drive from Monterey to Carmel.
If you're restricted to the city you can do all the touristy things. If you have a hire car, head up Leavenworth Street from Market Street towards the Fishermans wharf area. Nothing special about the street except that it's so damn steep that as you go over the crest and down the other side you feel as if you might need to contact air traffic control.
If you're in Union Square, head down to Market and take the cable car to Hyde. Try and time it so that you can get to the front of the running boards and hang off the handrail...childish, but good fun.
When you get to Hyde, head towards the water and turn right towards the Embarcadero. You can stop off at The Cannery which should be on your right, there is a little raised stage area where they have some excellent bands and singers on - you take pot luck over what style of music it is, but there are worse things to do than sit in the little courtyard with a beer listening to music. You can also call in at Jacks Bar right next door, where they have dragsters on display in the bar and a great selection of beers.
If you keep heading away from Hyde you come to Pier 39 and all that tourist stuff, worth a look as well.