If you are truly up to the big fridge cleaning, make sure to grab a new sponge or spongecloth to prevent bacteria on old cleaning devices to be be transferred to the surfaces you want to clean. Wipe the rubber seals on the door with a soft microfiber cloth.
Step by step
After turning off the fridge, pack out everything, not just the food, but all removable parts of the machine. Discard expired items. Clean the shelves and accessories in the dishwasher or in the kitchen sink.
Wipe the inside thoroughly with water and disinfectant from top to bottom.
It is important to also wipe the rubber seals thoroughly with a soft cloth, preferably a microfiber one.
Then let it air well, let the inside of the machine dry completely and finally pack everything back.
As a final step, wipe the entire machine from the outside.