Draw a picture or take a digital photograph of the item from which you wish to make the stencil. If you take a picture, upload the photograph to your computer, then use editing software to turn the photograph into a line drawing, and print it. If you are planning to make a large picture, resize it accordingly and print the picture in sections. You can also use a similar technique to resize line drawings by scanning them, resizing and printing. If you are using a simple line drawing that is the correct size, you can skip the electronic part.
Place a sheet of tracing paper over the drawing. Block out the "islands" in your picture, and connect them using thin strips, referred to as "tabs." The tabs will leave little lines when you spray paint or roller paint over the stencil; but these can be quickly brushed over during the painting process, if desired. Cut the stencil shape out of the tracing paper using sharp, pointed scissors. Embroidery scissors are useful for getting into small spaces.
Place the tracing paper over the stiff stencil material. This can be poster board or some sort of plastic sheet. Recycled file folders or discarded X-ray film make good stencil medium. Carefully trace the tracing paper stencil lines onto the stiff stencil material. Use an art knife to cut along the traced lines, taking care not to cut through the tabs holding the islands in place. If you are cutting a series of stencils for a large picture or mural, number the pieces to avoid getting them mixed up during painting.