Self Taught Cake Decorator

I have taught myself and watched others putting cakes together and on TV recentky since I was 16 years old and made my first wedding cake with Daisys all over it boy have I come along way now since then 34 years ago I have cooking and baking cakes I occasionally from time to time find myself with a cake that the sides don't look that great after dirty icing.  It looks like one pan was too small or too large and it sticks out on the side I use to think it was ok but now I want more uniform cakes How do I correct this problem? I have been shaving it off with the knife Am I doing this right or should I bake all in the same pan to make sure all my layers stack up more perfectly.