Piping on the frosting is a simple way to create various fun effects. To cover the cake in roses, use a star piping tip. Hold the tip perpendicular to the surface of the cake where you want the center of the rose to be, then apply pressure to the piping bag while swirling outward. Gently release pressure once the rose reaches the desired size. Do not alter the angle of the piping tip to allow for the swirls to fold over onto themselves, creating more dimension. To cover the cake in small stars, use a star piping tip, hold the tip perpendicular to the surface of the cake and pipe small dollops all over. For ruffles, use a petal piping tip and, starting at the bottom and working your way up, pipe around the outside of the cake with the wider end of tip up against the cake.