When I'm ready to sew a bunch of blocks together and need to keep track of the order, I print out a sheet that has "1A 1B 1C... 2A 2B 2C...", as much as I need for the job. I cut the labels apart with an old rotary blade and pin them in the upper left corner of the blocks. I throw away the labels when I'm done because it's too much trouble keeping them in order, but I keep the file with the labels for the next time.