When parking your vehicle on any hill:

When parking on a hill, you should always leave your vehicle in gear or in the "park" position. If there is no curb, you should turn your front wheels so that the vehicle will roll away from the center of the road if the brakes fail. If there is a curb, the front wheels should be turned toward it (if headed downhill) or away from and gently touching it (if headed uphill).
DMV Writen Test