Keep your gas tank over half full for added safety. In extremely cold climates consider installing an engine and/or battery heater.
Anti-freeze protection should be at least -25 degrees (50/50 mix 35 degrees).
Occasionally pour in a can of fuel line anti-freeze in very cold weather.
On cold, windy nights, park with the front of the car away from the wind.
On manual transmission cars, depress the clutch before engaging the starter so it doesn't have to turn the transmission gears which are immersed in 90W gear oil.
Door lock defroster is useless locked inside the car. Keep it in the house, purse, pockets or desk.
Tires deflate as temperature decreases one pound of pressure for every 10 degrees of temperature drop.
A 75 watt light bulb under the hood near the battery can help keep the chill off of the battery; this could help a cold start