|Eyes up. Watch for zombies.|
|Stay awake while your buddies sleep.|
If a survivor is on his own he is in for an entirely different experience. A person cannot keep watch over him or herself. In this scenario it is essential that you find a defensible location with limited entrances. (Make sure you still have your alternate escape routes.) A system of alarms will need to be set at every entrance to the sleeping area. Tripwires and cans are excellent for setting up a very basic alarm system. Anything that will make a lot of noise when hit is good. Zombies will not attempt to avoid such traps. They will walk into them. Hopefully you will be woken up. Blocking up all entrances in a method you can undo in the morning is also a good move. You are putting yourself at risk if you need to bang out in a hurry, but you are also less like to have that need.
No matter what your situation sleeping is a dangerous time. Just remember to make yourself as safe as you can be. Keep your weapon with you. Don't sleep out in the open. Don't be stupid. Survive.