Buy Quality Coffee Beans
You can't make a great cup of coffee without quality ingredients, so it all starts here. Specialty stores like Starbucks and Peets sell beans that have been roasted only a few days earlier, but you could also go with the roaster at your local grocery store or even buy bulk online. (If you do go online, be sure to check out the roaster's website to see how fresh its beans are.)
If possible, buy only what you'll use in two weeks--coffee that sits in your pantry for too long will start to lose flavors and aromas. Store it in a tightly sealed container away from light or moisture.
Measure the Coffee and Water Correctly
Fill your coffee maker's carafe with cold tap water to the level marked on the inside of the pot, usually 2 cups (16 oz.). If you're using an 8-cup model, fill it with 6 cups of water.
This is crucial. If the water level is off, your coffee will be underextracted (too weak), overextracted (bitter), or both. But don't measure the water in a measuring cup--use your carafe, because it's usually larger than a typical measuring cup and more accurate.
Over- and underextracted coffee taste bad--the former is too weak, the latter bitter. If your type of coffee maker doesn't go by weight, see our guide to brewing coffee for more tips on measuring correctly.
Finally, you'll want to make sure your coffee maker is clean. It's tempting to just fill it up with water and go, but residue from old coffees can affect the flavor of the next one. Run a cycle with just water through the maker at least once a week (any more often if your tap water isn't very good).
If you use an electric kettle to heat your water, make sure it's clean. Bacteria and mineral deposits can build up in or around the heating element. Fill it with a vinegar-and-water solution, then rinse with fresh water and let dry before using.