Based on some questions I heard recently, I thought I'd post some info about how actors and agents interact in the San Francisco Bay Area.
1) where do I find a 'good' agent?
Depends on your definition of good, of course. SAG (Screen Actor's Guild) lists agents here. Scroll to the bottom of the page, and then select 'San Francisco' as your city. There are 9 franchised agents, and one listed as non-franchised. I'm not sure that franchised/non-franchised makes a big difference for non-union talent. Given that SAG has chosen to list their contact info, I don't think any of these agencies are going to scam you. Some only rep very specific types, so doing a little further research into each agency and who they represent before you do a submission would help you know who to submit to.
2) can I have more than one agent at once?
While this may be the practice in other markets, where one agent reps you for commercials and another for voiceover, that doesn't really happen in SF. Your agent is your agent. Some people do move from one agency to another as their career grows and changes, but they still only have one agent at a time.
3) do you need an agent to audition for theater in SF?
Nope! If you're looking for theater auditions, start at Theatre Bay Area, but also check the websites of the theaters you want to audition for. Many hold general auditions at least once per year, often open to anyone who signs up.
I've been repped by an agency for close to 3 years now. They mostly send me on auditions for on-camera industrials and commercials, but I also audition for voiceover work (again mostly industrial and commercial, every once in a while a video game voice), and sometimes for print - not high fashion runway stuff, but projects where people are supposed to look 'real'. I also work every once in a while in print as a hand model.
I think a big assumption that a lot of folks make is that once they get an agent, they can sit back and the auditions and jobs will just roll in. Even with agency representation, you'll still need to work to build relationships, practice skills and develop craft. The difference is that now you've got someone else on your team who can put their foot in the door for you, and negotiate better compensation when you do get a job.