Here my top 5 tips for decorating sugar cookies with royal icing - 1. Whip the royal icing with an electric mixer until it's thick enough to pipe. 2. Use a very small round piping tip with a piping bag. 3. Practice a few times on parchment paper or the cookies that didn't bake up as pretty. 4. When filling in a whole cookie, outline it first then fill in most of the center. Use a toothpick to fill in the gaps and even it out. 5. When layering designs, allow the bottom layer to dry completely before piping on top designs.