When I'm doing a scrappy type quilt with blocks that are not all the same ... I lay them out on the floor or bed or design wall, and move everything around until I'm happy. Then I label them with little pieces of masking tape, identifying the rows with letters and the columns with numbers (A1, A2 ... An, B1, B2 ...Bn). Kind of like a spreadsheet.
Then I can always get them back into the right order if I lose track as I sew rows together.