I buy fabric very much like Butterfly Wingdoes - usually 4 yds so I have enough for the border lengths of the 'some-day' quilt. I don't like to piece borders. Turns out, it's a good thing now that I'm thinking about Stack N Whack, or One Block Wonders.
I keep backings separate from the rest of the stash, though I often make a special backing using fabrics from the front + muslin or other stash additions. I usually use muslin for Wall Hanging backings.
I have FQs from my 'landscape quilt' days. FQs are now eftovers, because I make very few now. Sometimes use them in Paper Piecing.
I sort by color. I TRY EO REMEMBER to hang muslin covers over my bookshelves full of quilts when I'm not working - not to keep dust off, but to keep the sun from fading the edges. I learned that the hard way. I definitely do it when I leave CT for AZ in the winter. My AZ stash is in a closet behind closed doors.