Pick up your sign material at a local art or sign store. If you're going to display the sign outdoors, it may be best to purchase acrylic or PVC signboard to ensure it can stand up to the elements. Make sure the signboard is large enough to fit the text at a size that will be sign from a good distance away.
Decide on the message your sign will carry. While many people are content to write "No Trespassing," others like to make their signs funny or frightening. What you choose depends on what works for you and what fits on the sign.
Write the text on the sign in large block letters using your pencil. This will allow you to plot the complete design of the sign without worrying about making a mistake. If you find that your artistic skill leaves something to be desired, you can use letter stencils or a ruler to make straight, even letters.
Trace over your pencil sketch with markers or paint. For most sign purposes, a permanent marker is more than enough to get the point across. Large signs may be easier to make with paint.
Punch a hole in each of the top corners of the sign with a pencil or other sharp object, straighten the clothes hangers and insert them into the holes. These will work as a simple way to hang your sign on a fence or rail.