So, the reason the first step is cardio because you have to be able to out-run a zombie in lot’s of situations. Good cardio means that you would be able to outrun and get away from zombies that are chasing you. That’s why good cardio is necessary to have because who wants to get caught being slow.
Trigger finger is important because most zombies will not die from just one hit unless it's a shot to the head, and it will instead get up in very little time - and will then bite