How to clean your microwave oven
1.    Mix four cups of water with lemon juice in a large microwave safe bowl
2.    Microwave on high for 3 - 4 minutes
3.    Remove the bowl (careful: it will be HOT)
4.    Wipe the inside of the microwave with a clean cloth.
Dip a sponge into the vinegar-water solution and use it to wipe food stains off of the walls of the microwave.
There are two alternatives to lemon juice:
Ø    If you can’t get lemon juice, try vinegar.
Ø    If you have run out of vinegar, cut a lemon in half and place both halves cut-side down on a microwaveable dish with a tablespoon of water.
How does it work? Heating water with the lemon juice, lemon or vinegar steams all of the food off. Acetic acid in the lemon juice, lemon or vinegar sanitizes and deodorizes your microwave.
It’s as cheap, effective and simple as that! So why not give it a try. This is one way to avoid commercial chemicals that people are using to do the job.
Repeat the process if necessary to get rid of stubborn spots [In other words, if it’s been years since you gave it a real clean out].