I have a much easier way to join binding ends than Marci Baker. I fold over the beginning of the binding into a triangle: the "Magic Triangle". I start sewing with 6 to 8 inches of the binding free. You can pin that tail in place so it is where you want it when you need it. Also put a pin or two where you want to stop the sewing, about 6 to 8 inches from the tip of that triangle. When I come around to the end, I stop sewing at the pin and pin the binding down where it needs to be. Lay the two pieces of binding ends over each other. Find the base of the triangle and cut the end off there. Now your binding overlaps only as much as your binding is wide, no matter how wide it is. Sew these two ends together in the same manner you sewed all the other seams in the binding. Right sides together and twist to the plus sign, but keep all edges even, nothing sticking out. Be sure the fold line goes across, not into the corner and tip. Sew on the fold of the triangle, and you have your binding ends sewn perfectly! Press the seam open and trim.
Do this a time or two, and you will never sew your binding together any other way.