Hi Shayne: Jay J is correct, there is much written out there. I myself have written so many responses to this on various boards that my fingers are sore. The answer to ice daming is a long one; dealing with building a thermal envelope in your attic, to ventillating (or not ventillating) to bitumen sheeting. The concept in not difficult, but the alternatives and how to do them is long.
Just remember....no roof is designed to be water proof...only to shed water. And if your insulation and ventillation are correct, you should never get ice.....even in deep snow (the worst condition for ice daming)