As NW75 has pointed out, three key things to take note:
1. Always keep the battery warm, cold temp kills your battey very fast.
2. Condensation. Allow your camera to "defrost" slowly inside a zip-lock bag. Avoid placing it next to a heater or fire place. Sudden fluctuation in temperature is harmful to your equipment.
3. If using a tripod, try to use CF instead of metal. A few seasoned CSers here pointed out the nasty frost bite.