What an interesting thread. When I read the question I had to read the rest to see what folks thought. DogHouseMom's information was excellent.
My only addition is to visit as many quilt shops you can, feel the fabric (has a fine hand), check the back, see if it comes off the bolts evenly (not pulled crooked as it is printed or put on the bolt which is important if you have prints), and learn the names of the fabric companies, i.e. RJR, Moda, Hoffman, Kaufman, etc. Each are a bit different, but once you get comfortable with the company, you will feel more comfortable ordering from an online shop that has that company's fabric, especially when it's on sale!
Experience will be your teacher -- but the most important thing is enjoying the subject as so many of us do.