Grab that free, low-hanging fruit
These strategies may sound simplistic, but they work well:

Turn down the thermostat. "The rule of thumb is that you can save about 3% on your heating bill for every degree that you set back your thermostat" full time. Turn down the thermostat 10 degrees when you go to work, and again when you go to bed -- a total of 16 hours a day -- and you can save about 14% on your heating bill.

Use fans wisely. In just one hour, a hard-working bathroom or kitchen fan can expel a houseful of warm air, according to the Department of Energy. Turn them off as soon as they've done their job.
Keep the fireplace damper closed. Heat rises, and an open damper is like a hole in the roof. Also, limit use of the fireplace, since fires actually suck heat from a room. Close off seldom-used rooms. And shut the vents inside.
Turn down the water heater. Lowering the temperature of water in the water heater to 115-120 degrees reduces power use often without a noticeable difference to the user.
Keep heating vents clear. Vents blocked by rugs and furniture prevent heated air from circulating efficiently.
Use curtains. Opening curtains and shades on south-facing windows during the day allows solar radiation to warm a living space; closing all curtains at night helps retard the escape of that heat.

Swaddle water heater and pipes. Unless you've got a newer water heater that already has built-in insulation, covering your water heater with an insulated "jacket" will keep costs down, especially if your heater is in an unheated place like a garage. Also, wrap water pipes when possible, especially when they run through uninsulated areas.
Winterize windows. If you can't afford storm windows, put plastic film on those windows where a clear view isn't crucial, which will curb drafts and keep windows from rattling.
Buy a low-flow shower head. A water-efficient shower head can use 25% to 50% less hot water, saving both on water and power bills, with little to no reduction in user satisfaction.
Buy a smart thermostat. If you're the kind of person who forgets to turn the temperature down at night and before work, but who doesn't mind programming things like the TV remote control, a "smart" thermostat can be set to change the temperature for you.

Keep your furnace in shape. "It's amazing how often a heating or air conditioning unit stops working because an air filter is clogged. Replace the air filter according to manufacturer's directions and your heating system will operate more efficiently. Oil-fired boilers should be cleaned and tuned annually, and gas systems, every two years. By maintaining your heating unit, you can save between 3% and 10% on heating bills.
Look for other insulation opportunities. Some well-placed insulation, especially in the attic of older homes, can save a bundle in rolls from 22-32 feet, depending on insulation value).