I've never had an unplanned overnight stay, but have done a fair bit of winter camping over the years. #1: Do NOT drink alcoholic beverages, as it lowers your core body temperature. That warm feeling of euphoria from drinking spirits is just that - a feeling. #2: A Bivy sack can help save your life, but you must take care as to not be overdressed when in it, as sweating will leave you colder.#3: Easy fire - Take cardboard strips and roll into a shoe shine tin in a circular motion like a burner tightly, then melt parrafin wax into the tin. Light and compact, will burn for several hours. Flint / magnesium fire starter is a compact item that can light a hundred fires if used properly. If you wish to learn a bunch of winter survival skills, try to find a copy of the Scout Handbook, read it and practice the skills. Carry the gear as if you plan to stay the night every outing. It may be a bit bulky, but it may be the difference between surviving or not. Be prepared, not a statistic.