First, I make sure the quilt is pressed and opposite sides are equal. If not, I fix them. For straight borders, I am lazy about sewing then cutting. This works because of the first step and my very even pressure in combining the parts. I use both methods for miters, "depending". For pieced borders, if I need a fudge factor, it's generally in inner border strip, although sometimes I design something to put into the middle of the border to serve that purpose, generally also reversing the direction of the border in its middle. (Flying geese flying towards each other, for example). I use just about eery form of corner, but I think I use cornerstones more often than not.