Hold a lit match or lighter near window frames and notice where the flame flickers, indicating drafts. Cover those windows with plastic sheeting, using a blow dryer to seal them to the glass, or staple the plastic to the outside window frames. Seal the areas where the sash meets the frame with weatherstripping tape or spray foam that can be peeled off in the spring. Use door snakes, or stuff blankets under inside doors that open onto unheated rooms or porches.
Wrap your electric hot water tank in a blanket or a wrap specially designed for that purpose, available at all home improvement stores or through your local power company. Set the tank's thermostat control to 120 F. Equip your hot water tank with a timer that heats the water only when you need it, or turn the tank off at the circuit breaker panel each night.
Unplug all devices such as toasters, coffeemakers, printers, phone chargers, blenders and radios when not in use, as they create a slight energy drain. Turn lights off in unoccupied rooms or install motion lights to limit how long they stay on. Install compact fluorescent light bulbs in lamps and ceiling fixtures. Use several low-wattage nightlights to brighten dark hallways and bathrooms.
Have your heating system overhauled by a professional technician every year. Move heat from wood and pellet stoves to other areas with small fans installed in the top of a doorway leading out of the stove's room. Open drapes on south-facing windows during sunny winter days and close them at night.
Look for unlikely ways for the cold to get in, such as holes that water pipes pass through, open spaces under kitchen counters, spaces around chimneys, and electrical outlets on external walls. Pack insulation in any openings and cover unused electrical outlets with clear weather-stripping tape. Wrap water pipes with foam insulation to conserve heat and prevent them from freezing.
Reduce the number of times the refrigerator or freezer doors are opened. Bake or roast several food items at once to maximize the oven's usage. Store water in jugs for drinking or cleaning to reduce faucet usage if you have an electric water pump. Use a slow-cooker instead of a stove to prepare foods that need a long cooking time. Dry clothes outside if local codes allow it or use indoor drying racks instead of a dryer.