I will usually buy 2 yards if I find a fabric that speaks to me.. and trust fabric talks to me a lot. My MIL and Aunts send me a lot of fabric also so I have a very large stash. I try to color code. In my quilt room I have all my batiks on shelves of their own. I have a 7footx4foot cabinet with glass doors that house all my batiks. large yardage of backing materials are hung in the closet and I have 2 large book shelves that house the rest of the fabrics. I have a dresser in the closet for all the velvets,silks and satins I am saving to do a crazy quilt.
Now I have 4 large binders on a shelf. I cut a 2 inch swatch from all the fabric I have and staple( if its a FQ I cut a smaller swatch) it to a form I created that has, date of purchase, where and how much and who the manufacture is and how much I have of it.
(hopefully I have all that information :).
One day I will scan it all into the computer. Maybe.