Yard Signs are most commonly made with corrugated plastic, a cost-effective and waterproof/weatherproof material good for year-round use.  Standard size for yard signs is 18" tall x 24" wide.  Of course, custom sizes are available.  Other common sizes you may see are 16x24, 24x24, 24x36, and 36x48. 

There are several options for finishing your yard sign.  The first option is to use a Standard H Step Stake.  The stake fits into the corrugations of the sign, and the other end is pushed into the ground.  For larger signs, two H Stakes can help anchor the extra material. 

If you plan on hanging the sign, another finishing option is to have grommets (reinforced holes) punched in each corner, or at regular intervals along the edge.  This allows you to easily strap a sign to a fence or wall.  Real Estate Signs are usually hung on an arm with two grommets at the top.

Other variations of the H Stake and Metal Frames can also give your sign a polished look while anchoring it securily to the ground.