This is one of the trickiest questions to answer. There really is no great answer but there are things you can do to make yourself more appealing to a booking agent.
First, develop a good website.
Knowing a good graphic artist is a great resource in this arena. Some sites I like are:
www.bigego.com
www.tmbg.com
or, for a less artistic idea,
www.katietodd.com
Second, get some people or sites to link to your website.
I would look at:
www.Communitymusician.com
www.garageband.com
Third, have a great press kit, complete with pro photos, press clippings, and your good demo packaged well. Maybe submit that demo as an ep to
www.allmusic.com. I know a lot of booking agents in Chi-town look to see if you're there before they guarantee you money.
Lastly, investigate alternative settings for music. Can you play bars in crappy parts of town? Would you solicit to a bar that normally doesn't have music if you can do an acoustic jam on a weeknight? Can you play college parties? (Look for college online papers and maybe submit an ad for a band looking to help students rock out their weekend ragers.)
Ok, that's a start. I would definitely get onboard with establishing a web presence so, when someone who hasn't heard of you types your band name into google, they have to ask themselves how you managed to escape their attention.
Oh, yeah. have good marketable music and lots of paying fans.
miles