How do you use a piping bag effectively for decorating cakes and pastries?

To use a piping bag effectively for decorating cakes and pastries, first choose the right tip for the design you want. Fill the bag with frosting, leaving some space at the top. Twist the top of the bag to push the frosting down to the tip. Hold the bag at a 45-degree angle and apply even pressure to pipe the frosting in a steady motion. Practice on a plate before decorating the cake or pastry.