OK, Snail; from my own experience (often repeated):

I phone the organiser of a club where I've had a successful gig last year and ask if (s)he'd like to book me back this year. The reply: "We've had to cut down on our guest nights. We can't fit you in this year but we'd love to fit you in next year." I'm currently taking bookings for spring 2010.

Will- there are open-mic clubs all over the place where young singer-songwriters can go and strut their stuff to each other. Do these ever book paid professional or semi-pro guests? Do they accept people singing traditional material? Talking, again from my experience, the answers are "no" and "no".