Eat a lot of carbs the day before. Carbs give long term energy which allows your body to function longer. Avoid booze and caffeine. Eat well and don't load up on garbage.

Take an aspirin an hr or so before you head out. Aspirin thins the blood and it will help your fingers and toes stay warmer because the blood will flow easily through the capillaries. Take an addition aspirin every couple of hours. Stay hydrated.

Wear layers and make sure none of the layers are too tight. You need a dead air space for insulation. If you have a military surplus store handy see if they have any military issue extreme cold weather gear. It works very well and is designed to survive rough treatment. Always wear a hat and good gloves. Turtlenecks are good because they seal off the neck. Baklavas are worth their weight in gold and WindStopper is worth its weight in diamonds!
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