With our Joann's, unless I have something specific in mind, I just wander. Usually I hit the rolled remnants, then just go down the middle aisle toward the quilting area and just look, glancing at sales along the way.
With my LQS, I have a list most of the time and look for colors and fabric that will fit that list. The LQS has very little sales, they are usually in one place, so I gravitate toward those.