How do you steer a mountainboard?
You steer a mountainboard by carving toe-side and then heel side making what we call J turns. Turning further up the hill will make the board slow down and eventually stop.

How do you stop a mountainboard?
Turn the board real sharply uphill and you will stop the board. Also you can use a hand-held V brake but it is best to learn to stop without a brake by turning and powersliding. Like a hockey stop on ice skates.