First, purchase a straw wreath wrapped in plastic. They are $2.99 for a 14" wreath at A.C. Moore, like 1/3 of the cost of a similar sized styrofoam one. I don't know why since they're much sturdier and have an overall more appealing shape.
Second, cut long strips of a fall-colored fabric and wrap them around the wreath, knotting each new piece to the already wrapped ones like so:
If you leave the plastic on, you will avoid getting stabbed by renegade pieces of straw, which is always good.
Third step, create a few fabric flowers from loose bits of fabric, old jeans, t-shirts, anything that matches your fall motif. All you have to do is cut two inch wide strips and twist them, keep twisting and they will curl in on themselves to create these delightful flowers. Then hot glue those bad boys to your wreath and VOILA:
I braided some of the leftover fabric to hang the wreath with, but I probably would have preferred to use a really pretty piece of ribbon. So there you have it! Enjoy!