5. Check your tires
Not everyone needs snow tires, which are soft, have tiny slits (called siping) to aid traction, and wear out quickly on warm, dry pavement. But your tires should be in good shape when winter begins. Keep in mind that half-worn snow tires are as good in winter conditions as a set of brand new all-season radials. Half worn all-season tires are only as good as a set of new summer tires. If you're running a set of worn summer tires, you might as well be riding on drag slicks. They're completely worthless in winter weather.
6. Practice makes perfect
If you live somewhere where it snows a lot—or at all, really—it's not a bad idea to find a vacant parking lot in which to practice driving in the white stuff. Hit the gas, slam on the brakes, jerk the steering wheel. Slide the car and spin it around to see what those things feel like and how best to straighten out. This will help you learn your car's limits. If something goes wrong out on the road and you find yourself losing control of the car, hopefully your practice sessions will help you regain it when it matters. Just look out for curbs and light poles in your practice lot.
7. 4WD doesn't give you superpowers
On snow-covered mountain roads, it's always amazing to see how many of the vehicles that end up sliding off the road are equipped with four-wheel drive or all-wheel drive. It gives a driver more control in some situations, but can also breed overconfidence. It doesn't help that many four-wheel-drive vehicles, trucks especially, are taller and more likely to tip if they hit something going sideways.
8. Plan for the worst
This is particularly true if you live in a cold place. If your luck runs out, have a few supplies on hand in case you have to sit around in the car for hours on end waiting for help. These include snacks, water, blankets, winter clothes fit for the outdoors, and a folding shovel, at the very least.