good snow tires (Nokia or Hankook, forget the Blizzak advertising crap) and maybe 75-100 lbs of sand or tools in the trunk, and keep the tank near full. A limited-slip diff is nice too. I drove my 530i for 12 years @ 365 days with all the performance mod's that should make it handle like a pig in the snow - they just made it go better. Just make sure you have the appropriate oil in the engine for cold weather and renew the antifreeze and thermostat. PS the heater might not work very well at -40 degrees.