If you use a reusable coffee filter with your drip machine: Go, you! If the most you do to clean said filter between uses is bang it around above a trash can: Go give it a proper cleaning right now, you!
Here's the thing about coffee makers: They get way grosser than you realize, with hard water buildup, mold, and bacteria. (Related: Roaches in Your Kitchen? Check the Coffee Maker) So you do need to clean them on a fairly regular basis. And that includes the filter basket.
See, in addition to that other stuff, filters can accumulate a buildup of oils from the grounds as the coffee brews. Those oils can turn rancid and, eventually, make your coffee taste bitter, sour, or even metallic. Not exactly the three top words you think of when you imagine a morning cup, right?
So, beyond dumping out all the grounds into your trash can (related: 5 Ways You Can Use Leftover Coffee Grounds Around the Home), you also need to clean the filter. Use warm, sudsy water after each daily use and just make sure you really rinse the basket well to get rid of soapy residues.
Then, once every in a while, let the filter soak in a bowl filled with one part water to one part white distilled vinegar. (These are the same supplies you'd use to clean the rest of the coffee maker, too.) Let it sit for 30 minutes and then rinse the filter under warm water.
P.S.: While we're talking about filters, now would probably also be a good time to swap out your Brita pitcher filter, if you haven't done it in a while.
Do you use a reusable filter in your coffee maker? When was the last time you cleaned it?