Shop for a fridge with the freezer on top. These use about 10 percent less energy than side by side refrigerators. Avoid units with automatic ice makers and water dispensers in the door. They burn about twenty percent more power than other refrigerators. Whether you buy a new fridge or not, make sure you clean the cooling coils on the back and bottom of the fridge.
Dirty coils work harder and use more power.
Check the seal around the door, too. If the door doesn't shut tight, consider buying a new gasket. Finally, location matters as well. Don't put the fridge in direct sunlight or beside hot appliances like stoves or ovens.