If you're wondering how to prepare for something like this may I suggest reading a very interesting book? With all due respect to the FReeper of the same name, "Alas Babylon"^ by Pat Frank is a must read. Frank wrote this book in the late 60's. It's the story of folks in a small town in Florida and how they survive an atomic attack from the former Soviet Union.Granted, atomic attack causing national destruction is much less likely today and the Soviet Union no longer exists. But the book still does an excellent job of portraying what these folks go through and the fruits of planning and not planning.
I have read this book many times, it's one of my favs. And I have used it as a "how-to" guide in my personal preparation for "what if."