The best thing to do is go see bands that play a similar style of music so you can get a feel for the crowd and the venue itself. Then introduce yourself to en employee and ask them who books the bands and how to get in touch with them. If you get the opportunity to meet with the person who does the booking, make sure you have a professional looking promo kit containing songlist, names of other venues you have played, (even if it was with another band), some club owners will want hear your band so it might help if you have a good quality recording and some owners want to know how many people are in your band. There some owners who might prefer that you send them a link to a website where they can see and hear your band. Keep in mind that many clubs will not pay for a new band and might ask you to take the door. The bottom line is that they want bands that draw a crowd. They make their money by selling alcohol not by booking bands.