Depending on what I think I will use it for 1 FQ up to 1/2 yard if I want just a little to add to scrappy quilts, 1 1/4 yard for borders and 4 yards for lap quilt backing or 6 yards for twin backing.
I always buy atleast 1 FQ or 1/2 yard. I do not get 1/4 or 1/3 yard cuts as I find people do not cut straight and it is not as usuable. With 1/2 yard cut I can use 1 FQ and have one FQ left instead of a remnant.
I have been buying way more 1 1/4 yard pieces for borders as I have a real good foundation in FQs and for backings I tend to buy sales as it is such large quantity.