The Sewing Bible by Ruth Singer.
Here's my mitering breakdown:
2. Do it again. (And if you want to stop here, just sew a line all around as close to the edge of the fold as you can.)
3. Fold down a corner like you're dog-earring the page of a book. Iron. [Picture of this step to be uploaded in the next day or two.]
4. Now, open the corner back up and fold the two adjacent sides together. See the nifty little line that you made in #3?
5. Sew right on that line. Trim the seam allowance to just about an eighth of an inch from the hem.
6. Open it up, push the point out, and now sew down the seam as close to the folded edge as possible. Et voila!!!