There a few basic, but very important principles in extracting great tasting coffee. These principles (and a few tips) will serve you much better than a rigid set of instructions.
Before we jump right in, it helps to think about what coffee really is and what we want it to be. Essentially, coffee is a drink composed of the extracted components of the coffee bean... not bitter, but fresh, hot, and strong.
Fortunately, you don't need great skill - you have to avoid messing up.
In my personal order of importance:
- Clean Coffee (Clean Equipment)
This is the easiest to mess up, and it can also make the greatest difference. Even if you can only improve one aspect of your coffee-making experience, paying attention to this can provide great results.
Essentially, we want fresh and clean coffee. Essentially, coffee has a fair amount of oil in it, and this oil can go rancid. Some people are used to this and don't notice it - but trust me, you'll notice a difference once you fix this and you'll find you can't go back.
Clean regularly every component that touches coffee or coffee beans and grounds; Hot water helps make the grease flow, but soap may be needed to truly remove all the oils. However, any amount of soap in coffee will ruin it, so you'll need to rinse it very well (use hot water) after washing. Avoid using the coffee decanter to pour water into the top of your drip coffee maker, as you may be adding small amounts of coffee remains that will likely remain for the life of the coffee maker.
- Don't burn it!
Coffee is a mixture of different chemicals - water being the biggest, but as I mentioned there are oils and oil-soluble good-tasting stuff inside the coffee. Coffee is best extracted with a water temperature near but below boiling, but once the coffee is extracted, it should be cooled a little further. Otherwise, these great-smelling, great-tasting components of coffee will quickly break down - removing what you want and adding an off-taste that you don't.
So, avoid using the hot plate! Many people have cheap drip coffee makers with glass carafes and hot plates. Many restaurants and even places like Tim Hortons have used them (which is why the coffee is made every half hour). Alternately, simply turn off the coffee maker as soon as it is done - the sooner, the better. Even better, just get a coffee maker with an insulated carafe and you can keep good coffee for a long time, and it won't go bad just by sitting there. Tip: Pre-heat the carafe with hot water.
- Good-tasting water
Since most of coffee (99%) is the water you start with, it's important to use a decent water source. For instance, filtered or distilled water will not have many of the minerals that can give coffee a bad taste. (find a more eloquent / better explanation online)
I use brita-filtered water, since my tap water is pretty good in general.
- [Fresh] coffee beans
This usually the first thing people think of. To preserve the delicious volatile elements, keep it in bean format and grind it just before use. Also, keep it sealed away from oxygen and moisture for freshness. Storing it in the fridge may be counter-productive; that may cause water to condense and spoil your coffee faster, so just use a sealed container at room temperature.
- The right temperature water for the right period of time
You want to extract the good tasting components from the coffee bean, but avoid the bitter ones. Fortunately the bitter ones are extracted last. Use water slightly below boiling, and tune the contact time between the beans and the water. (In a coffee press, you'll want 2 - 4 minutes of steeping time, depending on the grind size) This may take some experimentation.
If you use a drip coffee maker, this doesn't really affect you as:
- You can't really control the temperature, and
- It's already optimized to the right temperature for you anyways
However, you can affect the coffee-water contact time (and therefore the bitterness of the coffee) by the amount of coffee grounds you use (more coffee -> less bitter), and the filters that you use. (e.g. using two instead of one will increase the contact time) To dramatically shorten the contact time, this may be more effective: Use less water in your coffee maker, and add near-boiling water to the finished coffee to dilute it to desired strength.