I usually try to use the same fabric as my backing. I cut it 8" wide and whatever the width of the back of the quilt.
I then hem it on both ends so it is inside the binding.
I fold it, wrong sides together, lengthwise and sew it into a tube.
Iron it with the seam in the middle of the tube. You are going to be putting that against the backing so it won't be showing anyway.
I usually have my binding sewn onto the front of my quilt by now. I then sew it across the top on the same seam as the binding.
I then turn my binding and hand sew it in place. It secures the top and has a nice finished look. (if the binding is already done, just whip stitch it across the top right next to the binding.)
Next, I hand stitch the bottom and the sides. On the sides, you just stitch the bottom of the tube to the quilt.
Your finished tube will be about 3 1/2 inches wide. Then you don't have to worry bout what size rod is being used.
I hope all that made sense.