Blog. Seriously. Blogging has been by far my most useful business development tool. I'd say about 95% of my work comes unsolicited through my blog. The other 5% are projects I find listed on job boards like
http://www.authenticjobs.com And those are just the projects that look like something I'd REALLY want to do. I'd advise against trying "not to turn anyone down unless you're too busy". I've learned saying "no" as much as you say "yes" works better. You gotta pay the rent, but bad clients who don't pay, or don't know what they want, aren't going to help make that happen. Here's a site with some GREAT examples of designers who blog - you'll never guess what it's called...
http://www.designers-who-blog.com/