Sunshine! Windows on the south side of the house get the most sunlight. Eastern windows get sunlight in the morning. West facing windows receive sunlight in the afternoon. Open shades and drapes during the daytime and close when the sun goes down.
Correct air leaks around windows, doors and electrical outlets.
Repair weather stripping and caulking.
Check your threshold for any gaps between it and the door. Use a bottom seal that can be attached to the bottom of the door - it should brush up against the floor to seal up the threshold. It virtually stops drafts.
Keep radiators free of dust for top efficiency.
Turn your thermostat back when not at home. By turning your thermostat back 10 to 15 degrees for 8 hours, you can save about 5 percent to 15 percent a year on your heating bill - a savings of as much as 1 percent for each degree if the setback period is eight hours long.
Get an automatic setback or programmable thermostat, which, when used properly, can shave $100 off your annual energy bills.
Replace any cracked glass in your windows.
Seal off your attic-circulating fan with polyethylene and tape.
Make sure your ceiling has at least six inches of good thermal insulation.
Wrap your pipes, to guard against heat loss and prevent them from freezing.
Keep ductwork in good repair with duct tape or duct insulation. Your home could be losing up to 25 percent of its hot air before it reaches the vents!
Re-glaze window glass (glazing is the putty that seals the glass to the frame). You can use a putty knife or glazing gun. Re-glazing stops air infiltration on the sash (window frame) itself. You can then install a V-strip to stop any leaking that would go around the sash. This also makes the window easier to operate up and down.
Avoid using space heaters. They're expensive to operate, and can be dangerous, too.