I sort by size...and you don't want to know how OCD I am about it....oh alright I'll tell you. I have a plastic for every width from under 1 1/2" up to 6" in 1/2" increments.
The reason I go by size is when you are doing a scrap quilt and it calls for 2 1/2 squares, you take out your 2 1/2 " box and your 5" box. If you only need blue, then just take out the blue ones. That way you are not measuring to see if your scrap is big enough, and you are not wasting by cutting up larger scraps to now have more smaller scraps.
Yes I have a life outside the sewing room.