when i shop for a specific project i purchase 1/2- 1 yard ( or more if i love it think i will use it alot) extra - that way i have extra if i make any mistakes- and i have some to add to the fabric shelves.
if i am purchasing fabric just because i love it & think i will use it in the future i pick up 2-3 yards...more if it is a good background fabric i think i would use alot of (if the price is a deal)
i don't generally purchase pre-cuts- once in a while a charm pack if i want a little piece of a whole collection- or if i am using yardage of a collection and i want to add small amounts of the complete collection- i don't consider pre-cuts part of my stash- i seldom buy fabric just to add to my stash- i buy it for a purpose & enjoy the left-overs
