Plan the layout of your design in advance. Do a test run by taping the stencil to a piece of cardboard and filling it in as you will on the sidewalk.
Clean the sidewalk thoroughly with a power washer to remove any debris that could potentially interfere with your artwork. Let the sidewalk dry completely before beginning your design.
Lay the stencil in place on the sidewalk. Put a piece of multisurface tape on either side of the stencil to hold it in place.
Fill in the stencil with the medium of choice. Use spray chalk, which works like spray paint, for temporary designs. Standard chalk also provides an option. Apply spray paint for permanent sidewalk art. Blend colors together or fill in borders by running a foam brush across the sidewalk.