I do mine the way Bonnie Hunter (Quiltville) does. I cut strips the width of the border (not the length). I trim one end, fold the quilt in half, lay the border out along the folded center, align/pin one end, smooth out (do not stretch) along the quilt and trim at the other end. I do not use a measuring tape. My borders are never wavy using this method, and it's easier than trying to measure a long border. If the quilt I am working on is big, I will pin every foot or so along the way so it doesn't shift, then trim when I get to the end. Once I sew those 2 on, I refold the other way and do the same for the other sides.
Here is a link to her hints.
http://quiltville.blogspot.com/2005/...der-hints.html