Grinding coffee beans right before the brewing starts is crucial for a good cup of coffee.
Why? Taste the difference!
Coffee beans start to loose their flavors immediately after grinding. Exposure to air is devastating to both ground and whole bean coffee. An estimated 50% of the gases trapped within the coffee bean are released within 5 minutes of grinding.
Think about these comparisons that have equal weight to buying pre-ground coffee: Would you have all the beer or soda cans pre-opened at the store, so you don't have to hassle with it later? Have your eggs cracked open for you a couple of days before you want to use them? Or buy enough french fries to eat for a few days afterwards so you don't have to go out and buy more?
You can grind your coffee with the push of a button by electronic power, or using a manual grinder powered by you.
The cheapest electric grinders really chop, not grind. They have a spinning blade, similar to a food processor, that chops the coffee beans. These grinders can be found in most stores and tend to cost around $20. Blade grinders produce - yes, freshly chopped coffee - but the grounds are uneven which compromises the brewing results when compared to burr grinders. Don't let this be a cop out for grinding your coffee fresh. Using the the worst grinder in the world to grind before you brew beats the best grinder, pre-grinding your coffee beans.
Burr grinders produce much more even coffee grounds because they uniformly grind instead of chop. Also, you can adjust how fine you need your coffee ground. There are burr grinders with flat burrs and others with conical shaped burrs which are even better because they literally shave the coffee beans into grounds . If you are willing to invest physical effort in your grind, you can get a top of the line hand crank burr grinder for only about $50.
So, if you would like to improve the quality of your coffee at home, invest in a grinder. Once you have a grinder, you are one big step closer to the ultimate cup of coffee.