As previously mentioned a folding shovel should be included and even throw in a bag of sand if you have the room but don't have chains. These two things can really help you dig your car out if necessary.

Also...it has been mentioned once, but I am going to say it again...SOCKS. Your feet will get wet and you will need dry socks.

And get a tow strap. I truck capable of pulling you out may drive by, but they might not have a strap. I have seen this happen more than once.