In reply to Len: Copied this from an article in an outdoor mag a few years ago:
A sleeping bag should be used as part of a system which includes clothing,
shelter, food, drink and sleeping mat
Clothing
• Always change clothes at the end of the day’s activities even if you don’t feel damp / sweaty – get dry and warm!
Sleeping Bag
• Make sure it has a hood with a draw cord
• Consider a Liner
Sleeping Mat
• Very important to insulate between you and the ground!
• Closed cell is best on frozen ground, inflatable for comfort (or both!)
• Spread spare clothing on top of mat if necessary
Shelter
• Don’t pitch in hollows or valley floors – cold air sinks
• Make sure your tent is adequately ventilated to prevent condensation
Food and Drink
• Hot substantial meal and hot drink
Other
• It is easier to stay warm than get warm – get in sleeping bag early
• Get into sleeping bag with clothes on – then remove as you get warm
• Wear warm hat, gloves and socks
• Lay jacket on top of sleeping bag
• Make a hot water bottle
• If you wake in the night and are cold do something to about it – put on clothes, exercise, food etc.
• Consider a pee bottle?