I like scrappy quilts, so anything under a FQ cuts cut down into the biggest usable scrap sizes possible. I also like to put every last bit of fabric to use.
If the piece is big enough, I cut some 12-1/2" and 6-1/2" pieces I can use in the future to piece together for big block scrappy backings or use to make small blocks for my Dear Jane and 365 quilts. Then I start cutting 5" squares and 5"x2-1/2" blocks for some nickel quilts I would like to make once I get my UFOs under control. I cut squares in 3-1/2", 3", 2-1/2" and 2". Anything leftover either goes in the crumb box, the strippy box or gets chopped into confetti for pet bed filler.
Because I like random scrappies, I sort by size and not by color. I keep them an Ikea Trofast dresser. The drawers are actually plastic bins that slide out completely, so they are easily carried over to the machine when I need to use them.