First, brush all the crumbs that you can off of the cake. Use a pastry brush for this. Make sure your icing is thin enough to spread. Test it--if it wants to curl up around your spatula as you're trying to ice, it's too thick and needs to be thinned out with a little water, milk or other liquid. Once your icing is the correct consistency, apply a very thin coat of icing all over the cake. This is the "crumb coat." It is a coat of icing designed to trap any crumbs that might be lurking, ready to make your icing job all speckled and sad. Put your cake in its swanky new crumb coat into the fridge to let the icing firm up. After half an hour or so, you can add your final icing coat. Do the sides first with a small, offset spatula. You don't have to be very neat at this point. Just get frosting on the cake. Once the sides are all covered, hold your spatula 1/4" away from and parallel with the sides of the cake. Angle the spatula to scrape away extra icing. Then, slowly spin your turntable, scraping the extra icing into the bowl. Next, scrape/dump a ton of icing on top of the cake, spreading it out to hang over the edges of the cake by a little bit. Scrape extra icing back into the bowl. When the icing is as thick as you want it (maybe 1/3"),  perform the little sides-of-the-cake number again--just the scraping portion. What you now have is a cake with smooth sides and a little icing "perimeter wall" standing up maybe 1/2" all the way around the cake. Knock those edges down using your icing spatula in a sweeping motion from the edges to the center of the top, one section at a time. scraping all the extra icing back into the bowl. Now you should have a fairly smoothly iced cake to decorate however you'd like. Tada! Find all my icing and frosting recipes here.