To keep from buying something I don't really need, I have snipped off a corner of each of the fabric I have and glued them to paper - then I take it to the fabric store and get what I need. It also helps me when I put together colors.
Sometimes the prints are overwhelming in appearance and, since I can't picture a small piece, I bring a manilla folder that I have cut several 2" squares into, place the fabric I'm considering side by side on the table, place the "holey" folder over it and get a fairly clear picture of what it would look like.
Did this with blues for the bluebonnets I'm getting ready to start. By the way, looks like San Antonio is going to lose a bunch of Hancock Fabrics - and they told me that Joann's is cutting back on their fabrics, too. Anyone know the scoop on this?