Other than cutting pieces a scant larger and aiming for a scant 1/4 inch I don't focus on the actual seam allowance. However I do have a six inch ruler that I use to check my finished units. If they are off then they get a redo. I'm very hard on myself, I may let a 16th inch off go but that is the limit. My goal is to always do my best, or if it's difficult, do the best I can. That said I haven't finished very many quilts.