Thin your icing with a few drops of water if it seems too stiff. Spoon icing into a pastry bag fitted with a fine writing tip or into a paper piping cone. (To make a paper piping cone, cut a piece of parchment or wax paper into a 15x12x8-inch triangle. Starting at the short corner, wrap the triangle up along the long side to make a tight cone. Fold the tip into the cone to secure it. Spoon icing into cone, close the top of the cone and fold edges over to seal. Cut a small opening in the tip.) To outline a cookie for accent, pipe a continuous line or a series of connected dots around it.