We did this tour on the first day of our first visit to San Francisco and it was a great Introduction.
The walking tour lasted 6 hours. Our guide, Dara, kept it interesting, which made the time fly by. We started on Fisherman's Wharf, by the cable car turntable and finished at Union Square, where you are given a ticket for the cable car (an absolute must), back to Fisherman's Wharf. In between we did North Beach, Chinatown, the Financial district and The Embarcardo. Caught the Metro to the Tenderloin, then a tram to Union Square.
We really enjoyed it. Dara was an interesting guide. Would highly recommend this tour.