Keep all vents in fridge and freezer clear of anything like food containers or bags and debris. Blocking vents can cause excessive ice buildup, damage components and make the fridge/freezer stop cooling.
Pull fridge out and vacuum the vents located at the bottom back of the unit. When the condenser coils are covered with dust, the refrigerator can’t run efficiently. On some models the coils are accessible from the front. This should be done twice a year or more if you have pets. If they are really dirty they should be serviced.
Keep door seals clean. Wash them with warm soapy water and a sponge. Avoid detergent as it can damage seals.
Refrigerators need “thermal mass” (lots of stuff) to maintain low temperatures. Cool foods and drinks help absorb warm air that streams in when you open the door. If your fridge kept mostly empty or is too big for your needs, store a few jugs of water in there to make fridge run more efficiently.
Keep interior clean. Use a cloth dampened by warm water to wipe down and remove crumbs and spills from shelves and walls regularly. An all-purpose cleaner will make the job easier for tough grime. Food particles can easily get into the drain and plug it causing water to leak from the fridge.