We use a typical drip coffee maker with a thermos-type pot. Naturally I rinse the pot and filter holder every day, but how often do I need to clean it more thoroughly? I've heard that it is bad to use soap and water, but is that just an old-wives tale, maybe out of fear that it could leave a soapy residue? Once a month or so, I'll run a few cups of white vinegar through it, which seems to improve the flavor a lot, but is a surprisingly expensive proposition. Any suggestions on frequency and method? 
It is bad to clean your coffee pot with soap because the soap can bind to the oil deposited from the coffee and can leave a taste behind. It's recommended not to wash any part of your coffee maker in the dishwasher for the same reason.  To clean your coffee pot fill it with 2 cups of ice, 1/4 cups of table salt, and 1/4 cups of lemon juice (fresh or bottled). Swirl it around the pot a couple times and that will do the trick. Hope this helped!  