1. Correct Coffee-to-Water Ratio:
Because coffee is a strong flavoring agent, it takes relatively little to produce a robust brew. The generally accepted ratio is 1.0 - 1.5% coffee to 98.5 - 99% water.
2. A Coffee Grind That Matches the Brewing Time:
To prevent under- or over-extracting the flavor from the beans, you must match the right particle size (grind) with the right brewing time. In general, longer brewing times should be paired with larger particles and shorter brewing times with smaller particles.
3. Properly Operating Brewing Equipment:
Because your brewing equipment controls the coffee's contact with the water, it is important that it be precisely calibrated and well maintained. In particular, you should pay attention to the length of the brewing process, the temperature of the water and the amount of mixing (turbulence).
4. Optimum Brewing Method:
To achieve the flavor you desire, you must first choose the right brewing method. There are six basic methods of brewing: Steeping, Decoction, Percolation, Drip Filtration, Vacuum Filtration and Pressurized Infusion.
5. High-Quality Water:
In general, water that contains 50 - 100 parts per million of dissolved minerals will produce the best-tasting coffee.
6. An Appropriate Filtering Medium:
A well-made filter is essential to clarify the beverage and separate the extract from the coffee grounds.
Source: Specialty Coffee Association of America