An oven is an expensive purchase and one that you should take care of.
Do not store plastic items or other utensils in the oven as they may melt or burn if the oven is accidentally turned on with them inside. Use large enough cooking pans to avoid boil-overs. If spills occur, wipe them up promptly.
Do not put large pieces of foil on the oven floor or racks unless the appliance manual recommends it. Then follow manual instructions as to the size and placement of foil exactly. Foil in the oven, especially on the racks, may slow cooking and reduce browning. Do not line broiler pans with foil, as it concentrates the heat and may damage the pan.
Fill a small glass bowl with ½ cup of full strength ammonia, place in the oven and close. Let it stand overnight, then wipe loosened dirt with paper towels or newspapers. If then necessary, rub surfaces with a suitable abrasive, such as fine steel wool or a soap-filled steel wool pad, wiping off "suds" with paper towels. Then wash with warm soapy water and rinse. Repeat the process if necessary.
Commercial oven cleaners are helpful if ovens are very soiled, but they should be used with caution. These cleaners can damage surfaces outside and around the oven. Be sure to protect these areas with layers of newspaper or other materials and cover your hands with protective gloves. If using most commercial oven cleaners, never spray in a hot oven (over 200 degrees Fahrenheit) which will make it even more caustic and can corrode surfaces. Never spray on the oven light, electric elements, or pilot light in older gas ranges. Turn off the pilot light when using spray oven cleaners.
Removable parts, such as broiler pans and racks, can be cleaned more easily if allowed to soak in a sink or pan of sudsy water to which a little ammonia has been added. A lot of soaking is better for the surface, and easier, than a lot of scrubbing. Never soak aluminum in ammonia or other alkalis.
If necessary, you can scour oven racks or porcelain enamel with steel wool or a scouring pad to remove baked-on grease or food spills that have not come off in regular cleaning. Occasional use of such abrasive pads, or scouring powder on badly baked-on soil is OK, but don't use these too often or scrub too hard for you can scratch the smooth surface and make it harder to clean from then on. Do not scour mirror-finished metals, glass, or baked-on enamel.