Use the first paragraph to introduce the band. Tell what your name is, where you are from, when you started and what sort of music you play. You can use examples of bands who influence you to help characterize your sound. Don't overdo it, though, no one wants to read a list of your twenty favorite bands.
Introduce the band members. Beginning with the singer or songwriter, discuss what each member plays and does, characterize her style and talk about her history. Tell what other bands she has played with and how extensively she has played. Give a brief but detailed image of what musical skill and experience every member brings to the band.
Give a history of the band. Describe what albums you have recorded together, what tours you have taken and with whom, any major line-up or stylistic changes, and anything else that seems relevant. You want to really give the reader a sense of your place in the local music scene.
Talk about your commercial viability. Discuss local shows you've had recently and how big a crowd you can expect to draw. Clubs want to know if you can bring people in the door to begin with, so don't be afraid to promote your following if you have one.
List what equipment you have. For some clubs, you will need to bring in your own PA and soundboard, and you may even need you own sound man. List him if you have one. You should also discuss what amps you are using and their wattage to give the club an idea of how loud you are. If you have lights or special effects, you can mention that as well.