Hi Jill
I think you have to approach and shop for booking agents the same as any other service or commodity.
The band I played in for years in Wisconsins often took jobs from a great booker who quite often got us a lot more money than we were able to get.
I also know of some solo acts around here that also get a lot more money through their booker than they can. Lots of times it's private parties that they would have never known about in the first place. I asked this one girl vocal/keyboard act what her agents get for commission, thinking it might be 10%-15%. She said she didn't know or care what he got because of the very high paying gigs, as in $500 worth for a single for just a few hours, which I don't think is too bad.
I used an agent a short time ago looking for work. She got me a gig right away about 3 days later.
I have also contacted several other agents in the area. They all need a promo package.
I feel that I am really doing more interviewing of the bookerthan the booker is of me. I feel my demo speaks for itself.
So, in short, I feel it's like shopping for anything else. I think anything is worth a try. I know I'm pretty good at reading people and spotting a BSer. But, even then, you may not know until you give it a try.
Right now I am checking into bookers a lot farther away than I originally planned to travel, only because the local bookers are basically confirming what I have found out myself, which is, at the present, there is not really that much work around this area.
Do what you like, but I personally think anything is worth a try.
Best
Scott Langholff
http://www.ScottLMusic.com