I think, in the first place, it’s important to have sufficient skill and experience to perform at the correct level. If you’re crap the punter and venue will be quick to let you know.
Assuming you’ve got the goods, then having the professionalism to communicate well with venues, market and promote the gigs is a major selling point.
Lastly, simple things like turning up on time to gigs, being affable with the staff/organisers, talking with the punters before and after the performance consolidates a good impression and helps secure future bookings.