Frosting a Cake
One of the most basic tips (and perhaps the most important) is to be sure to let your cake cool completely before frosting!
With a long, serrated knife cut off any “bumps or humps” so that the cake will lay flat on the plate and so the second layer will lay flat on the first layer.
Brush off any loose crumbs before applying frosting.
Use a flexible palette-knife-style spatula to apply the frosting.
Use 1/2 cup frosting for between the layers. Then frost sides and finish with the top last.
For a smooth finish you can dip the spatula in hot water and gently run it around the sides of the cake to smooth the frosting.