One way to clean all that stuff that sticks to your microwave is to take about a tablespoon of baking soda (bicarbonate of soda) and put it in a microwave-safe bowl filled about half full with water. Microwave for about three minutes ONLY and the stuff wipes right off. (see warning below)
Another way is to wet a towel and place it in the microwave and cook on full power for 30 to 40 seconds. The steam that comes off the towel will loosen any hardened stains. You can use the heated cloth to wipe the inside clean. Be careful though it will be very hot
Yet another way is to boil a solution of 1/4 cup of vinegar and 1 cup of water in the microwave. Will loosen splattered on food and deodorize.
Warning: It is important not to heat fluids in your microwave for long periods as they can become super heated, this can cause an irruption within the fluid even after the vessel has been removed from the microwave. This irruption can send scolding super heated fluid in your direction.