For proper extraction, grinding properly is essential. Freshly grinding coffee before brewing is one of the most important steps for achieving a quality cup of coffee. Coffee should not be ground more than 2 minutes before brewing or major staling (oxidation) begins to take place.
There are two main types of grinders available. Blade grinders sell for about $20-$40, grind the bean unevenly, and are messy. Burr grinders are priced at $60-$125, grind evenly, and are clean and easy. The burr grinder is a great investment for improving cup quality and one's sanity.
For any scientific analysis, a blade grinder is unacceptable due to its lack of reproducibility.
Burrs should be replaced periodically (every 600-2000 lbs of coffee), but for typical home use, it is only necessary to clean the burrs.
Each brewing method requires a different grind size: drip coffee requires a medium size grind, espresso requires a fine size grind, a French press requires the largest grind size, while the vacuum pot also requires the largest grind size. For cupping, it is preferred to use a French press size.