Metateps

Make sure the fridge or freezer door shuts tightly. If not, clean or replace the seal. Keep the condenser coils clean (they're in the back or bottom of the fridge), using a vacuum or brush. If it has an energy-saver switch, turn it on.

Keep the fridge and freezer out of hot rooms, out of the sun, and away from heating vents and heat-generating appliances, like ovens, dishwashers, and space heaters.

Keep the freezer compartment full, but don't block the fan that circulates the cold air. A full freezer takes less energy to keep things frozen. Fill empty space with water bottles. If the power ever goes out, they'll help keep the freezer cold, and you can transfer a few of them down to the refrigerator to keep it cold too.

Maintain the refrigerator temperature between 34 and 40 degrees F, and the freezer between 0 and 5. Any colder than that is a waste of energy. The only way to be absolutely sure is to have a thermometer in the compartment. They're cheap and available at any discount store.