I empty the refigerator, turn off the power and let come to room temperature with the door open (avoids condensation), scrape or clean out dried food or other residue, remove and wash shelves and drawers in warm water and baking soda, then wash interior of refrigerator with warm water and baking soda, and let dry, then cut back on the power, hang the shelves and drawers, and put the food back in.
If I had serious mold or concerns about bacterial contamination, I would wash with warm water and white vinegar, or diluted bleach, then follow up with a warm water wipe down, then with a baking soda and warm water scrub. As Tomer1 said, bleach is more effective than vinegar. However, both vinegar and bleach have a smell that you must eliminate completely before putting the fridge back in service, or food will absorb those odors. Bleach is particularly smelly and is more difficult than vinegar to rinse off. Hence the final wash with warm water and baking soda. You'll probably need extended open door airing time if you use bleach or vinegar. And be sure to put an open box of baking soda in the fridge when you return it to service.