Keep your energy usage and monthly bills low by following these tips:

• Set your thermostat as low as comfortable in the winter and as high as comfortable in the summer. 
• Keep the temperature fairly constant, as frequent changes will utilize more energy by causing unnecessary cycling on and off. Setting back the temperature at night, however, is recommended.
• Clean or replace furnace filter before it obstructs air flow.
• Use a vent damper on natural draft (non-powered) combustion gas exhaust systems.
• Oil-fired boilers should be professionally cleaned and tuned once a year. Gas-fired equipment needs to be checked every other year.
• Clean warm-air registers, baseboard heaters and radiators as needed; make sure they are not blocked by furniture, carpeting or drapes.
• Keep draperies and shades on south-facing windows open during the heating season to allow sunlight to enter your home; close them at night to reduce the chill you may feel from cold windows.
• Close the door to an unoccupied room or area that is isolated from the rest of the house and turn down the thermostat or turn off the heat for that room or area.
• Use kitchen, bath and other ventilating fans wisely. Turn these fans off as soon as they are no longer needed. In about one hour, these fans can pull out a houseful of warmed or cooled air. They can also pull dangerous furnace combustion gasses into the house in some situations.
• Check your ducts for air leaks. First look for sections that should be joined but have separated and then look for obvious holes.
• Do not use standard cloth-backed duct tape to repair leaky ducts because it has proven to fail sooner or later. Various mastics or non-cloth-backed tapes are preferred.
• When looking for new household products, look for ones that have earned the ENERGY STAR. They meet strict energy efficiency guidelines set by the EPA and DOE.

Source: Consumer Energy Information: Energy Efficiency and Renewable Energy Network, U.S. Department of Energy.