There are tons of cold thread out there but here's a summary:
1. Quite a few dead heaters due to super cold because the heat pumps had been working down to 30-40*F but the resistance heaters were dying below freezing.
2. Assuming the heaters are working, preheat
3. Range on cold batteries is seriously reduced from summer time experience. Gunner down around Omaha (Iowa side) hasn't reported any problems during a Christmas trek from Omaha to Jeff City Mo and back.
4. Garage your Leaf to help keep battery warm during night.