At the beginning of the game, Jack notices a stranger standing in his yard.. The game will instruct you to go out and confront him. Instead, go upstairs to the attic and find your .22 rifle. The zombie will start to bash his way into your house, but it is better than running up to him unarmed, as he will almost always bite you. Also, the key to the shed in your backyard is in the basement. If you go downstairs before coming into contact with the zombies, you can get a revolver, ammo, and a hammer from the shed. These make it a lot easier to fight off the walking dead at your house, and you can complete the level twice as fast.