My criteria, after finding a fabric that just jumps out at me, is pretty much the same as the others. It has to be reasonably priced so I can afford it, but it also can't be thin!!!! If I pick up a fabric and I can see thru it, it isn't worth my time, effort, or money to buy! Trust me, quality matters as far as the end product is concerned.
I will go to the LQS looking for a particular fabric, usually a background fabric or something for a particular quilt, but mostly I buy what appeals to me or what I need in order to round out my stash. Most people collect a lot of medium value prints and the lights and darks are neglected. I'm guilty of this and when I go to a quilt store I try to keep this in mind. At the next shop hop around here in May I plan to concentrate on buying mostly dark, dark fabrics to build up my stash. Otherwise, I don't really have a plan.
I love the "Grab & Run" comment. :lol: