Any good cupcake always has a good frosting. There are many different types of frosting, but the most popular is buttercream, which is is just that: butter that has been creamed with sugar, creating a spreadable rich frosting that's perfect on cakes and cupcakes. The secret to buttercream is spreading it on completely cooled cakes or cupcakes soon after you make the buttercream. Never frost with too-warm buttercream or too-cold buttercream. Be sure to chill the cupcakes after you've frosted them to ensure the frosting stays firm and shapely.
Piping bags and cake decorating tips aren't even necessary for frosting cupcakes, though they are great for adding pretty flourishes. To frost, simply start by putting a big dollop of frosting on the cupcake and use an offset metal spatula to shape it into a mound. Then if you decide to decorate the cupcake further, you can decorate with your choice of tip to pipe a pretty design onto the already frosted cupcake. That's how you will get a prettily decorated, high-frosted cupcake that's sure to impress everyone.