A garbage disposal is a wonderful thing, when it is clean, well-maintained, properly installed, and working properly. When it malfunctions, it can be a nightmare. Once you have your sink piled high with post-celebration dishes and are expecting to rinse the residue down the drain, you do not want to hear a grinding noise followed by a "clunk" and a backup of funky drain water. That bad disposal is also likely to have a breath like a Horrible Halloween Ghoul, which will make matters worse. To avoid such a problem, make sure you have a good garbage disposal, properly installed, and then maintain it well.
A lot of garbage disposal maintenance is common sense and listening to what your mother told you. Actually, some of it may be not listening to what your mother told you, if she was one of those that put all the food scraps and leftovers down the disposal. Sorry, but you can't do that without suffering the consequences. Therefore, a lot of garbage disposal care is what you don't do.
You should not put horribly fibrous things through the disposal, especially in large quantities. Things like celery stalks, artichoke leaves, corn husks, even big piles of onion peels, can make a wad of fiber that will cause a problem. It is not a good idea to clog the disposal with grease either. That could combine with the fiber to form a plug that will lead to a plumbing emergency. You should use the correct amount of water at the proper time. Start the water first, put the scraps through the disposal with plenty of water, and allow the water to run a bit at the end of the session.
Really, cleaning is accomplished by using the unit properly, but you can also give it a boost with a couple of home remedies. You can put some baking soda down there and follow up with some hot water. That might help loosen a few stray bits that otherwise could cause a function or odor problem. You can also use a little bleach, but be sure you have good ventilation in the kitchen when you do. That stuff is toxic. For a stale smell or worse, you can grind some citrus peel through the unit. That always smells great, and lasts a while too.
Keeping the plumbing leading away from the disposal working properly is part of keeping the disposal working properly. That is probably a job for a plumber, and you may wish to call a plumbing professional in once a year or so to make sure that everything is working properly. Good maintenance can prevent a garbage disposal problem or an even greater plumbing disaster later on.