Most of my stash is sorted by color - well, the part of it that isn't laying all over the rest of the house that is. :oops:
I rarely buy fat quarters - and then they're usually for a gift or an exchange at guild.
Mostly I now buy 1 yard minimum & if one really calls to me & is on sale (I try to only listen to the ones on sale!), I'll buy multiple yards. I think it would be a great idea to mark your fabric as to how big each piece is, but for me, I just wing it. If I don't have enough of one, I either go scrappy or find something I have more of. :D