If your coffee consistently comes out weak or bitter, odds are, your coffeemaker needs cleaning. Fill the decanter with 2 cups white vinegar and 1 cup water. Place a filter in the machine, and pour the solution into the coffeemaker’s water chamber. Turn on the coffeemaker and let it run through a full brew cycle. Remove the filter and replace it with a fresh one. Then run clean water through the machine for two full cycles, replacing the filter again for the second brew. If you have soft water, clean your coffeemaker after 80 brew cycles — after 40 cycles if you have hard water.