Learn what to look and feel for. large chain stores do carry some quality fabrics but you have to feel it, check the draping and how much light comes thru it when held up to a light. If you can see your hand thru a fabric it is most likely too thin to quilt with.
I do avoid most fat quarters at chain stores. They seem to be really inferior.
I have also seen bad fabric at LQS. So learn what to look for.
peace