Snow and by car?

Know the laws of the country you're in.
You can get high fines when you don't have winterties on your car in Germany. The Dutch dont mind.

When bad weather is expected it's announced on the radio. So know on which radiostation it's broadcasted.

Check if your car has got the legal stuff available and put in what might come in handy: like a battery lamp (check the batteries), an emergency sign, a first aid box. Don't forget food and clean water.

Throw a few sleepingbags in the back.

And luxuries, like a book.