Food produces heat for your body. Fluids increase your blood volume, which means that extremities will freeze more slowly. Surprisingly, your body can demand more water in the winter than the summer. However, some beverages can actually cool your body more quickly. Caffeine is a diuretic and will cause you to lose precious fluid.
Alcohol opens the blood vessels in the skin, making a person lose heat faster.
Don't rub your hands together to warm them up, at least not if you have frostbite. Rubbing will cause more tissue damage. Give the victim aspirin thawing will be painful, and aspirin helps prevent blood clotting. Seek medical attention. Remove wet clothing.