For starters, I bought rolls of tulle...Joann's had them for $2.50 for a 6" x 25 (or 15) years roll. The dress pictured took 3 rolls!
Next, you'll need elastic. I used some scrap elastic I had kicking around my craft room. The wider (to about 1/2") the better...this way it does not (hopefully) roll. You'll only need enough to go around the subject's upper torso.
Now you can either staple or sew the ends of the elastic together...trust me this is all the sewing you will be doing!!
Now measure how long you want your dress. Then you will want to double that and cut the tulle into lengths that size. Once you have a bunch cut, you can start on the dress.
First take your lengths of tulle and fold in half, lengthwise. Then you are going to take the loop side (pointing up) under the elastic circle. Then tuck the other end through the loop and tighten, forming a "knot".
Continue this until you have used all your cut tulle. If it's not as full as you'd like cut and add more. I add as much as I possible can! I even get fancy and add alternating colors of tulle or ribbon!
When you are finished you can add a tie at the waist, some sleeves (I glued these to the elastic) or even get really wild and add some jewels!! I want to try this! (The one above has ladybugs glued to it)
The tutu will get tangled as it is taken on and off, but you can untangle it by running your fingers through it and "combing" it out!