Add powdered sugar a little at a time
Chill the frosting in the refrigerator
Beat in a small amount of cornstarch
Add more butter or cream cheese if the recipe allows
Mix in melted and cooled chocolate for chocolate frosting
Whip the frosting longer to incorporate air
Use less liquid next time
Add meringue powder
Let the frosting sit briefly to firm up
Avoid overmixing if it becomes too soft