1) Not knowing what to do next
Confusion is your enemy in a zombie apocalypse. It causes you to waste valuable time while whatever disaster going on around you gets worse and, the worse things get, the less likely you’ll be to escape them unscathed.
How does it happen? Plenty of ways, a few of which I’ll cover a little later, but, rest assured, circumstances will likely occur that can cause you or your group (Or any group of people you happen to be stuck in) to become confused as to how to deal with whatever dangerous situation you find yourself in.
How to avoid it?
Because so many situations can be very specific, I can’t cover every possible dangerous scenario you could face, but, regardless of what the scenario is, you need to know that it’s a possibility and attempt to have a plan in place in the event said possibility becomes a reality. The more dangerous or probable a possibility is, the more a plan for it should be a priority.
Furthermore, because you can never completely predict what will happen, it pays to try to imagine the most likely ways your plan can get screwed up on you, and then, figure out a secondary or even tertiary plan in the event and of those unfortunate possibilities emerge to disrupt your original plan.