Camp in high places, facing the sun. Do not climb heights in order to fight. So much for mountain warfare.
If you must camp high, doing so facing the sun will provide more warmth to compensate for the cold (although armies can hide more effectively in the shade).
It is good to be in high places to fire down on an enemy below, but fighting in high places is difficult unless you know the terrain well. It is harder to move and the crags may hide enemies who know the territory better than you.