Pull everything out and discard what's expired.
It's easy to clean around the shelves and doors in your fridge, but until you really pull them out, you'll never get that bit of spilled Diet Coke out of the rails and then you'll never be able to open your vegetable crisper without first playing tug of war. (I know this from experience!)
Use a clean cloth and a mild detergent, or mix your own baking soda/hot water elixir. Be as thorough as you can be, and remember the hotter the water, the easier spills will come up.
Be very careful when handling slippery, heavy glass shelves, and be sure to get into every small crevice.
Haul out a clean, dry cloth for this job.
Clean your food. This is a silly idea that is entirely necessary.
But you know your work is not really done until your food is arranged by color, location in the food pyramid, and/or alphabetically.
Keep some baking soda in the fridge and freezer to keep odors from overwhelming, and always remember to seal your food tightly before sending it to cold storage. Always, always wipe up spills promptly.
If you use ice cube trays (i.e. you don't have an ice machine), try to keep the ice fresh. Old ice is a known harbor for smells. And always wipe down your jar of jam before sending it back home to the condiment tray. Jam gloop is the worst!