You're talking about meeting the corners, right? Stop sewing 1/4" from the corner, backstitch a bit. Turn the binding the way you have to for mitered corners (up, down, etc). I have read to sew from the very edge of the new side, but I find that if I need to pare down the bulk at the point that the stitching is in my way, so I begin 1/4" down the new side, starting with 2-3 backstitches. What does everyone else think out there?