Close the damper on your fireplace when it's not in use. Fireplaces can create drafts and draw valuable heat up the flue. Check the seals around your windows and doors and apply the necessary caulking to prevent energy loss. Leave your storm windows on all year long. They provide valuable year-round insulation.
Storm windows can create substantial fuel savings.
Apply weather stripping to all exterior doors. As with windows this will prevent drafts and energy loss. Check the insulation in your ceilings and walls. Homes without proper insulation use twice as much fuel to heat as a home with proper insulation. If your crawl space or basement is heated cover any opening with polyethylene film or use storm windows and doors.