You have to make yourself smart, tough, and mean.  And you have to have a group of people with a similar mindset.  You cannot survive alone.  The biggest question in my mind would be do you dig in or stay on the move.  I keep myself in shape, have enough supplies to last 10-12 months and have identified the handful of people i will want to team up with and trust.  All that and you still may perish in the first 30 seconds.