You can check to see if you are getting a good seal by closing the refrigerator door on a dollar bill. If you can pull it out without resistance, replace the gasket. On new fridges with magnetic seals, put a flashlight inside the fridge some evening, turn off the room lights, and check for light leaking through the seal. Unplug the extra fridge or freezer in the garage. Move your fridge out from the wall and vacuum its condenser coils at least once a year.
Some models have the coils under the fridge.
With clean coils the waste heat is carried off faster, and the fridge runs shorter cycles. Leave a couple of inches of space between the coils and the wall for air circulation. Defrost your fridge if significant frost has built up. Turn of your automatic ice maker. It's more efficient to make an ice in ice trays.