You may want to use ski poles at first while you learn how to snowboard. Some teachers believe this is a good way for beginners to avoid wrist injuries. Learn how to use ski poles from a teacher who knows this technique, because snowboards are not actually designed to be used with ski poles. Most falls in snowboarding are on the hands, buttocks and head, and only cause bruises and soreness. Protect your wrists.
Most snowboard injuries are to the wrists.
Wear wrist guards made for snowboarding or in-line skating. Don't break your fall with your open hands. Hold your hands in closed fists while you snowboard so you won't be tempted to break your fall with an open hand. Try to roll into a fall like a paratrooper would, spreading the force of the fall out over your body instead of taking all the force in one place. Protect your head.