I use scraps of muslin fabric that I pink the edges. I used a permanent marker to write row numbers and block letters. I pin them in the upper left corner of each block so that I know which is top of block. When I no longer need them-after the quilt is assembled I put them back in order and store them in a plastic container until needed again. I have found that keeping everything in order-from the cutting process until the top is put together is important to me. So I use lots of labels and lots of pins to hold them in place. As I cut I make labels that coordinate with the cutting instructions and then change the labels on sections of blocks, then the blocks, etc.