5. Pack a Survival Kit
No one wants to think about the worst case scenario, but winter weather can often turn a simple roadside breakdown into an unpleasant battle against the elements. If your car strands you during a snow storm or on an isolated rural highway late at night, you could be in for a long wait for a tow truck. With the engine off, your heater won't be able to keep you warm, so during the winter months it's a good idea to keep at least a warm blanket (or two) in the trunk. You might also want to throw in some chemical heat packs you can crack open and stuff in your boots, some bottled water (it won't freeze right away, and you can always suck on the ice to fight thirst) and some extra batteries to power a small flashlight.
A small shovel that can help you dig out of a snow drift, an extra pair of gloves (if your current pair get soaked through) and a set of socks are also a good idea. Remember, it's all about staying warm, dry and protected from the elements until you can be rescued, or until the plows have cleared the road enough to get you back on the pathway home.