In "Sunday Morning Quilts" Cheryl Arkinson and Amanda Jean Nyberg begin the book by advising on how to sort scraps and keep them sorted going forward. They recommend sorting at least by colour, sizing/trimming pieces according to your own quilting style. Once you get the initial sort done it is easy to keep things sorted. I had already begun sorting all my scraps by colour, and got busy sorting the last of the bags of scraps I had. I have a line of those wire cubes below my biggest design wall, each containing a different colour. Makes it really easy to find what you need for and to work in monochromatic themes!