Since aphalt is less forgiving than snow, there's more incentive to nail your turns on a skateboard than on a snowboard. Find a long skateboard and a longer, dry, smooth, uncrowded stretch of road this fall, to improve your snowboard balance and control this winter.
Just as in snowboarding, bend your knees to keep your center of gravity low and over the board in the belly of the turn (see "right"). Maintain this low stance throughout the turn. Then stand up slowly (unweighting) and drive your body forward into the next arc.
For balance, keep your elbows close to your body and your hands in front of you in an athletic stance. Unless you crave high-speed death wobbles, don't bend at the waist like a pecking chicken (see "wrong"). Square your hips with the fall line, keeping your body moving down the hill.