Spray baste helps tremendously! Another thing I do sometimes is to use water soluble thread and baste every foot or so (each block of rows). This helps hold it together a bit more than the spray baste alone. I use a large stitch and do a simple grid every 12-18" inches or so. I always do my stitch in the ditch first, then quilt the blocks. I rarely have any puckers. Once the quilt is all done, I wash it and the water soluble baste washes away.