Question the Pros - The best way to be successful in the art business is to ask the advice of people who have already succeeded. There are a number of ways to do this both virtually and in person.
To start, take advantage of the Etsy forums and their "Quit Your Day Job" series. Though forums can be bogged down with people wasting time and chatting about who knows what, some posts can be extremely helpful. I find that the "Business Topics" section is best for useful advice. Many successful artists post in that section and are quick to share knowledge with newbies.
The "Quit Your Day Job" series is a string of stories featuring people who were able to make a full-time living from their art business. They share the ups and downs of making a full-time living from their art. It's useful to hear what has helped in their success and also what challenges they have faced in the process.
Participating in art shows is another wonderful way to pick the brains of seasoned art pros. Get to know the people participating in the event and ask them about their businesses. Each person will probably be able to offer something useful, and it never hurts to network (see N).
Taking an art class can also expand access to other artists in the area. Look for community art classes that target art educators and art business people. These classes can provide invaluable information and help you to network with many other artists and art educators.