If I think about it, my stash is totally made up of fabric I came upon that was at a good price.
Ok, so I see fabric at a good price. If I love it, and the price is extremely low compared to the quality, I usually buy 5 yards. As the 'love' goes down, and the price goes up, I might buy up to a yard.
I very rarley buy fat quarters, except one time they were .99, and were a good quality so I bought quite a few. Since then, there have been several times that I'm glad I bought them (it is soooo not in my nature to buy a quarter of a yard, no matter how they cut that quarter)