In reply to Toby S:
I've lived in some cold countries in my life (including Canada, where we had snow and ice on the roads for five months each winter) and attended several days of winter driving and skidding training on an old airfield. I would say the key things are:
(1) Fit winter tyres (or have chains with you): they make an all the difference.
(2) Always carry in the car a good selection of snow and ice scrapers, de-icing fluid, good winter outdoor gear including good mountain boots in case you have to get out and push your car etc.
(3) Always scrape and brush off as much snow and ice as you can from the outside of the car. This does not take very long, and one has not got to do it too thoroughly: if the sun comes out, and you have the windows clear, the interior will warm up and clear the rest of the snow and ice off the vehicle even if the temperature is far below freezing. If you leave the car covered in snow and ice, it will remain like an igloo; and the snow next to the car will turn to ice making it much harder to remove.
(4) Winter-driving Golden Rule 1: move your hands from standard 10-to-2 position to 9-to-3 and then never feed the steering wheel at all. Keep your hands glued to the wheel at 9-to-3. This way you always know where the neutral position of the wheels is, even if you can't tell by the feel (because of the lack of friction of the tyres on the ice). You need 9-to-3 to obtain enough movement of the wheel when your arms cross and meet each other.
(5) Winter-driving Golden Rule 2: keep your eyes on a position on the road far ahead of the car. This way, combined with the first rule, you will automatically steer the right way in the skid (without thinking about steering into or out of the skid, whatever that means: you don't have time to think anyway).
(6) Drive really gently and hardly use the brakes at all.
(7) If you do have to brake, pulse the brakes like an ABS system, so they don't lock the wheels up: with practice you can do this as well or better than ABS.
(8) For sustained cold, put a lower viscosity oil in the drive train.
(9) When parked, leave the mechanical hand-brake off, because it can freeze up.