Well, it seems that in this terrible dystopian world that the author paints for us in this wonderful novel, there are two options for you to adopt in order to survive. You become one of the "bad guys" and start collecting and killing other surviving humans to eat them or you go on the run and try and avoid the "bad guys" as best as you can. One of the reasons why this book is so powerful is the way in which it contains a number of disturbing descriptions of the way that humanity has descended into chaos as it literally feeds on itself. Take the following example of a group of the "bad guys" that the father and his son see:
An army in tennis shoes, tramping. Carrying three-foot lengths of pipe with leather wrappings. Lanyards at the wrist. Some of the pipes were threaded through with lengths of chain fitted at thir ends with every manner of bludgeon. They clanked past, marching with a swaying gait like wind-up toys. Bearded, their breath smoking through their masks.
The description goes on to describe how after these soldiers come the women, lots of them pregnant, and then a number of young boys kept as catamites for sexual purposes, all chained and being dragged behind them. This is just one example of how humans have tried to survive. For another you might want to remember how the people in the house kept humans in their dungeon to feed upon.
Of course the other alternative is modelled by the father and the son, and the family that the son meets at the end of the novel, who try to survive by scavenging and finding food without resorting to cannibalism.