One tip I received:
If you're not sure of the distinction between color value, fold, align and place the fabrics (or samples) on a scanner and scan in B/W.
Note: I purchased some fabric I thought would work for a quilt(after spending hours sweating over the selection). When I got home (away from the shop and in different light) I wasn't pleased with my selection. I went to my stash and found a great substitute. The fabric I pulled worked in my next quilt.