As you put the buttercream layers for the cake, make sure to chill it before you shape the cake and coat it with frosting.
Add crumb coat to secure the cake layers and make sure crumbs don't fall off or stick to the frosting.
Coat the sides and edges first then smoothen out the top to make sure there's even frosting everywhere.
Dip the spatula and shaping tools in warm water to keep the frosting from sticking to the spatula and result in a smooth finish.
A turntable allows you to see all the areas perfectly and leave no corner uncovered or naked.