To descale a Keurig coffee maker, follow these steps:

1. Remove any K-Cups from the machine and deactivate the auto shut-off if applicable.
2. Empty the water reservoir completely.
3. Prepare a descaling solution by filling the reservoir half with distilled white vinegar and half with filtered water (alternatively, use a Keurig branded descaling solution).
4. Place a large mug under the coffee outlet.
5. Start a brew cycle with the largest cup size and let the vinegar solution dispense into the mug. Pour the contents into the sink.
6. Repeat the brew cycle with the vinegar solution until the machine prompts for more water.
7. Let the remaining solution sit inside the machine for about 4 hours.
8. Empty and rinse the water reservoir thoroughly with soap and water.
9. Refill the reservoir with fresh water and run multiple brew cycles with clean water to flush out any vinegar residue.
10. Enjoy your descaled and clean Keurig!

For some newer models like the Keurig K-Supreme, there may be a special descaling mode you can activate by holding certain buttons; follow the manufacturer's instructions for those. Descaling is recommended about every three months or when the descale indicator light comes on. This simple process helps remove mineral buildup that can affect the taste and performance of your coffee maker.