I've always sorted mine by size, by width: I have drawers for 1in, 1.5in, 2in etc, up to 6in, beyond which I'd probably decide it was more than a scrap. I'll decide which width would make the best use of a piece, eg if it was 1in wide at one end and 2in at the other, it'd probably go in the 1.5in drawer. Triangles, I use the width of one of the shorter sides.
Recently though I've just left strips in the drawers and the rest are a glorious mix in a box, because I started making crumb blocks and wanted a random selection of colours and shapes!