There are a few good sites that show pics of the easy way to miter your corners. Here is one that I found--
http://quilting.about.com/od/binding..._binding_2.htm
Wish you lived closer! I'd come over & show you. Mitered corners are really so easy! (really), & they give a professional finish to your quilt.
Also work on a scrap piece before you go to your quilt. The practice will help & you won't have to do any frog work ('rip-it, rip-it')in case your first attempts aren't up to your satisfaction.
Good luck!