"If you’re in a performing (or soon-to-be-performing) band, then booking shows is a regular part of your life. Picking the venue, deciding on the cover charge, organizing the bands, choosing between bookers and a D.I.Y. approach—you’ve likely seen it all. But maybe you still have some questions."
Here's a really helpful article posted by our good friends over at CD Baby's blog, DIY Musician, that will help you get in touch with a venue, and find the best approach to get a gig booked.
http://diymusician.cdbaby.com/musician-tips/booking-band-at-venue/