Ive set up few shows, 2 or 3, so im no expert but I hope it helps. First you have to decide what kind of audience you want, and then look into booking a place that could have that kind of audience. It depends on what kind of music youre playing.

All you've gotta do is go ask the place about either giving if for free, or setting up some sort of deal where you promise to have a specific number of drinks sold. Or you could just pay the place and charge an entrance fee.

I think the hardest part is getting people to come, so just advertise a lot and tell you're friends to tell their friends to tell their friends....