It is very important that you wash your coffee maker pot and filter container thoroughly at least once a week. You should also do a light cleaning after every use. Bitter oils stick to the glass, plastic and metal creating an inferior final product.
If you are not going to wash your equipment every time you use your coffeepot put a couple of drops of liquid dishwashing detergent in the pot and run hot water into the pot. Let this sit on the counter till you need it again, rinse and you are ready to go. This does not replace the weekly or twice-weekly washing but helps keep your equipment cleaner between washings.
There are commercial coffee pot and espresso machine cleaners on the market that will do a very through cleaning of your equipmentÃ¢â‚¬â„¢s internal parts. For drip coffee pots you can use a solution of water and vinegar. Regardless of what you use be sure to get it completely out of the system. Commercial cleaners and vinegar will not improve your coffeeÃ¢â‚¬â„¢s flavor.
If you have exceedingly dirty coffee making equipment that will not come clean with regular washing the following procedure was suggested. If you have a coffee/teapot, the inside of which is stained with oily brown residues - also plastic/metal coffee filters, tea strainers, and stainless steel sinks in caffeine-o-phile houses - they can be restored to a shining, brand-spanking-new state by washing in hot washing powder (detergent).
Get a large plastic jug, add 2 or 3 heaped tablespoons of Daz Automatic or Bold or whatever, and about a pint of hot water - just off the boil is the best.
Swill the jug around until the detergent is dissolved, and then pour into tea/coffeepot, and let it stand for 5 minutes, swilling the pot around occasionally, just to keep the detergent moving. Put the lid on and shake it a few times (care: slippery + hot)
Repeat as necessary. Keep it hot with a little boiling water if needed. If you have a cafeteria, disassemble it, and soak the parts in the mixture for a few minutes, agitating occasionally.
In both cases, the residue just falls off with almost no scrubbing. It does great things with overused filter machine filters, too.
Important: Rinse off all detergent afterwards, use lots of fresh water!