After leveling up, open the "Character" menu. Scroll through the menu until you reach the "Skill" menu. Spend your first skill point to expand your skill tree to a few different paths.
Run across a map and begin kiting zombies. Get into a corner to increase the chance of damaging them all. Use an elemental weapon or ammunition (incendiary arrows, incendiary ammunition, explosive ammunition or electricity) to kill the group quickly.
Use Abbey and her skills to reduce the fall of food, thirst, and sleep as well as her +50% incendiary and explosive damage and +50% damage at night. Note: Build an Automatic Gun Turret by combining a Diving Tank, Short Tube, Motorbike Motor, Electric Device, and Hardware.
Fight a group of at least five zombies. After stunning them, press F as soon as you see the flashing instant kill message appears.