Simple question, complex answer.
Here are a couple of thought provoking, good references to start on getting the answer:
-James Wesley Rawles - How To Survive The End Of The World As We Know It http://www.survivalblog.com/writings.html
-Ragnar Benson - The Modern Day Survival Retreat http://www.scribd.com/doc/20580967/Ragna...ry-and-Practice
-Ragnar Benson - Urban Survival http://www.scribd.com/doc/32246591/Urban-Survival-Benson