What a cup of coffee can taste like is decided first by the beans. Grinding and brewing can only bring that flavor out; they cannot add what isn't there. Three things decide a bean's flavor.

• Origin sets the base: at the same light roast, Ethiopian beans lean floral and fruity, Colombian beans balance acidity and sweetness, Brazilian beans lean nutty and chocolatey. Within one origin, washed beans taste cleaner and brighter; natural (sun-dried) beans are sweeter and fruitier.
• Roast level decides which flavors are amplified: light roasts keep the acidity and aroma, medium roasts are the most balanced, dark roasts bring bitterness and body.
• Freshness decides how much is left: beans taste best one to four weeks after roasting. Buy whole beans, grind right before brewing, and keep opened bags sealed and away from light; ground coffee loses its aroma fast. When choosing beans, first decide whether you prefer brighter or more bitter, then look at origin and roast level.

Beans have to be ground so water can dissolve the flavor inside. The finer the grind, the more surface area the particles have and the faster extraction goes; the coarser, the slower. Each brewing method wants its own grind size: very fine for espresso, medium for pour-over, coarse for French press. Easier to overlook than size is consistency: uneven grounds make a cup that is sour and bitter at the same time. When coffee tastes sour or bitter, the grind is usually the first thing to adjust.

More than ninety percent of a cup of coffee is water. It is both the solvent that extracts and what you end up drinking. Water temperature sets the speed of extraction: 90–96°C is the usual range; too low and the cup turns sour and thin, too high and it turns bitter and astringent. The darker the roast, the lower the temperature can go. Water quality decides what can be dissolved: filtered soft water works best; very hard water tastes dull, and purified water has almost no minerals, so it fails to extract any depth. Water is easy to ignore, but it changes the taste as much as the beans do.

Brewing is where water and coffee grounds finally meet; everything prepared before shows its result here. The goal of brewing is to stop extraction at just the right point: acidity and fruit notes dissolve first, then sweetness, and finally bitterness and astringency. There are three variables to adjust.

• The coffee-to-water ratio decides strength: pour-over usually uses 1:15 to 1:17; the smaller the ratio, the stronger the cup.
• Extraction time decides whether you have extracted enough: too short is sour and thin, too long is bitter and astringent.
• The brewing method decides the texture: pour-over uses a paper filter and tastes clean and clear; French press is immersion plus a metal mesh, with more oils and a heavier body; espresso uses high pressure to pull a small concentrated shot in about half a minute. These three variables also interact with grind size and water temperature, so change one thing at a time; that is the only way to know which one made the difference.