Seal your Doors, Windows, and Attic
The small gaps surrounding windows, doors and other areas in the American house, taken together, are like a nine-square-foot hole in the wall, according to EarthWorks Group’s “30 Simple Energy Things You Can Do to Save the Earth.” Plugging them can save you up to 10% on that heating bill, and the materials will pay for themselves within a year, ACEEE says.
Air that you’ve paid money to either heat or cool is escaping from your home. The more air that escapes the more expensive it is for you. Cut down on both heating and cooling costs by plugging those holes and sealing those gaps!
Note: it is easier to find these leaks in the winter, as cold air is coming in. In the summer cold air is going out – so it’s harder to find the leaks.
Doors
Run your hand, or better yet a candle, along and near the door frame. If you can feel the cold air coming it you’re wasting a lot of heat here. if only the candle flickers isn’t not as bad – but air is still escaping.
To solve that get some weather stripping. It’s very cheap and a single roll should be more than enough for a single door – maybe even 2. It’s self adhesive on one side and will plug the gap where air is escaping with foam. Make sure to clean the surface before you apply the adhesive.
Use a door sweep to help seal the bottom of the door. 
Attic
Hot air rises – so hot air is escaping into your attic. if you have poor insulation you should add more. Use blown in insulation to fill gap.
Any holes in any ceiling (basement on up actually) should be sealed as well. Use expanding foam to seal the larger gaps, look around in the basement for large holes used to get pluming and electrical up to the floors above. You’ll want to push some foam insulation into those gaps or plug them with expanding foam. Remember, the goal here is to prevent air from going from one floor to the floor above.
Also – insulate the door into your attic as well. Use some of the weather stripping mentioned under doors to help seal the entrance.
Windows
Generally the same ideas as we had for doors above, weather stripping works great. Caulk the outsides of them as well.
Finally open the blinds/drapes/etc during the day to let sunlight in and close them at night to keep the heat in.
