Although this probably doesn't require a tutorial, I'm going to put it up anyways to really break it down. For this to work, you will need......
Freezer paper
pencils and sharpies
Scissors(it helps to have a small pair like what you use to cut thread or manicure scissors)
Fabric Paint
Fabric to Paint on
An Iron
1. Sketch out your design on a sheet of paper. It can be as detailed as you want, but it must be some sort of silhouette or it won't work. Its a good idea to draw with a pencil until you get the design just right and then outline it with a sharpie.
2.Place the freezer paper shiny side down on top of your design and trace it.
3. Cut the design out to make the stencil. Take an iron on a low setting and carefully iron your design to your fabric, shiny side down. The freezer paper should stick to the fabric.
4. When the paper/fabric cools down, carefully dab the paint into the stencil. Don't worry about getting paint on the paper because it will not go through onto the fabric.
5. Once the paint is dry, slowly remove the freezer paper and throw it away. You should have a design with nice, clean edges that you can use for virtually anything.
The designs on the sides of my Rapunzel skirt were each made from a giant stencil. I used this method and then did some embroidery on the outer edges to finish it off.