Are you what 'they' are looking for?

No matter how big or small your band may be, securing future gigs is key to survival. In a competitive field, like performing musicians, it's important to consider how your presence is marketing itself. So what does a venue look for in a performer?
Hosts need to make money. They make money in a variety of ways: ticket/cover sales, food/drink sales, and in more rare circumstances, advertising. Almost all of these avenues are directly impacted by foot traffic levels. Therefore, if they have a group come and play that brings in its own crowd they win.
Can you bring more people to listen, than would come with a band having its first performance? That's why marketing your name can pay huge dividends, even if your recognition isn't selling merchandise. Repeat performances in the same area, music giveaways, posting your name everywhere you can, these all help you create a solid fan base, which in turn bumps your desirability to play.
Professionalism. Be prepared with the right equipment needed, on time, and if possible, have a system to how you assemble yourself on stage. If the manager of wherever you are only remembers hassles and trouble when you last played, they are much less likely to want you back. In addition to the host, you will also have more time to socialize with the crowd and make them believe in you off the stage.
Remember to casually talk about your preparedness, and your follower crowd draw directly with you venue host. You want them to know, not speculate, that you have your stuff together and are worth the money.