Does this help? http://home-and-garden.webshots.com/album/578389110wAYXjW?vhost=home-and-garden
The best tip I found from Kaye Wood's site was this:
stitch at a 45% angle starting at about 3/8" before the corner.
The other was this:
those few small stitches help set n stiffen the corner.
Hope it helps, good luck.