It is better in most cases to cook longer at a lower temperature rather than the other way around.
To clean food baked onto the interior of the oven, heat a cup of water for about three minutes and then let it sit for another five minutes. The steam will help to loosen the food and make it easier to clean.
Even after the oven shuts off, the heat in the food allows it to continue to cook. Let food remain in the oven to allow more even distribution of heat in the food, or remove it from the oven immediately to prevent over cooking.
Point a container away from you when opening.
If your microwave oven is malfunctioning, try unplugging it for a couple of minutes. When you plug it back in it may reset and resolve the problem.
Don't repair your own microwave oven. Even when unplugged the capacitor has a deadly high voltage charge.
Never heat sealed packages or containers in the microwave unless instructed to do so.
Puncture food such as whole apples and potatoes so steam can escape.
Don't overheat liquids, they can virtually explode out of their container when moved or something is placed into the liquid.
Use a pot holder when removing anything from the microwave oven.
Never stand over a hot container when opening.
While there are cases in which metal can be safely placed inside the microwave, it should be kept well away from any part of the interior. Metal (this includes foil) also interferes with the microwaves even distribution, so the use of metal should be minimized.