Refrigerator
To check for air leaks in refrigerator door gaskets, close the door on a dollar bill or strip of paper in several locations around the perimeter of each door. If you easily can remove the bill (or it falls out), the gasket needs to be adjusted or, more likely, replaced. Also perform a visual check of the gaskets, looking for breaks or deformed areas that may not be sealing properly—or traces of mildew that indicate air leaks. Source: Iowa Energy Center.
Lighting
Turn off the lights when you leave a room.