how do you get the perfact frosting? i have tried many differents recipes and though the frosting taste good it dose not seem to have to right effect on the cake. if it is too thick it wont stick to the cake and if it is too thin it always gets messy when i try to put the fondant on. how to do you that thick icing to go under fondant and make your cake smooth???

You expriment with it until you find the right consistency - not on a cake necessarily, but even on a piece of cardboard or the outside of a cake pan. If your original frosting is too thick, add more liquid teaspoon by teaspoon until you like it. If it's too thin, add powdered sugar tablespoon by tablespoon until you like it. Once you hit it, you'll know it and then you'll be able to find it again and again. Unfortunately, recipes for things like buttercream are only approximate and the final recipe will be affected by things like temperature and humidity. I think this is what we've all done at one time or another.