How do I clean the inside of the microwave, especially baked-on food?

To loosen baked-on food particles or liquids, heat two cups of water (with lemon juice optional) in a four-cup measuring glass at High power for five minutes or until boiling, then let it stand in the oven for one to two minutes. Wipe up spills with a damp cloth and mild soap — do not use harsh detergents or abrasives. Keep the inside clean, as food particles and spilled liquids can cause the oven to work less efficiently. (Page 20)