if you are putting on a long arm, the seam usually works best if goes horizonally instead of vertical (think about rolling up paper after you put a string around the middle and then adding more--you always get a bit of a bump and the outside edges tend to crinkle and not lay flat--same with your quilt back). also, if you are not using blocks that are likely not to stretch cause of the seams in them, but instead using larger pieces of fabric, you get the best results if the larger pieces are all going the same grain--i.e. lenghtwise or crosswise, instead of a mix. Lenghtwise grain does not have as much stretch in it as crosswise does. sometimes with larger chunks of fabric mixed grains, you are more likely to get some droop in pieces that it causes puckers and tucks.