For winter use, a ceiling fan should spin so that warm air near the ceiling is pushed back down toward the floor. Think of the fan blades as scoops - you want the fan to turn so that the higher edge of the blade is in front, so it catches the air and pushed it down. If the blades slope upward to the right, you'll want the fan to turn clockwise when viewed from below; if the blades slant upward to the left when viewed from the side, set the fan to turn counterclockwise. Most fans sold in the United States should be set to turn counterclockwise in winter.