Cleaning the visible surfaces helps, but there are many parts of the machine that you can’t reach.
Surface Cleaning
Cleaning the outside surfaces of your washing machine with soapy water, a multipurpose cleaning spray or diluted white vinegar does wonders for its appearance. If you keep laundry detergent and other cleaning products on top of your machine, scrape off any thick, soapy residue before getting it wet so that you create fewer suds. If the detergent dispenser draw can be removed, do so and wash it in a sink of hot water. Otherwise, pour hot water through the draw and scrub it clean with a sponge, cloth or old toothbrush. The seals around the inside of the door need particular attention, as they often trap dirty water and lint. Wipe over all the inside surfaces you can get to with your choice of cleaning product and a cloth.
Vinegar Method
During an appearance on “The Today Show” in 2008, the editor of "Real Simple" magazine detailed an easy and inexpensive way to clean a washing machine: Pour a gallon of white vinegar into the drum and run a hot water cycle (without laundry). The vinegar neutralizes odors throughout the machine’s system, cuts through soap residue, and leaves the inside of the machine gleaming. You can replace the gallon of vinegar with two cups of bleach if your prefer. If you do use bleach, make sure the first load of laundry after the cleaning is a white one, just in case there are traces of it left. If your machine is really stinky, run a hot water cycle with bleach followed by one with white vinegar.
Washer-Cleaning Tablets
Commercial products designed to clean washing machines and/or dishwashers promise a foolproof solution: Just follow the instructions on the packaging. Usually, you place a tablet in the drum of the washing machine (without any laundry) and run a hot water cycle. The manufacturer of Affresh washer-cleaning tablets and cleaning cloths recommends cleaning your machine once a month.