Network - Networking is one of the most useful ways of finding new opportunities to sell art. Making friends with other artists allows you to pick their brains for useful art business information, such as upcoming art shows, selling tips and time management.
It is true that WHO you know is sometimes as important as what you know. You could be qualified for an art show, but maybe the organizers of that show know other qualified artists that they'd like to feature. Is it fair? Maybe not, but it happens all the time. It never hurts to get to know people that can advise you on your art career.
A key rule of thumb, as corny as it sounds, is to be friendly and pleasant to show organizers and other artists. If people think you are easy to work with, they will want to work with you again. Making a good impression is so important to securing future show spots.
Bottom line, don't burn any bridges. Your talent is very important, but no one will want to work with a talented snob.