Many people who drink coffee only occasionally at home or those that buy larger quantities tend to store their beans or grounds in the fridge or freezer. Unfortunately this isn't the best way to keep coffee. It may work well for fresh food, such as fruit and vegetables by extending their shelf life, but coffee ready for brewing isn't raw.
Coffee beans are actually seeds of berries and not plants or leaves. When green beans are roasted they essentially lose their water content and form sugars through the caramelisation process. Due to this the roasted beans will readily absorb water from the environment around them.
Fridges and freezers are moist environments and so coffee beans, but more so grounds, will absorb this moisture. Essentially this is the start of the brewing process, meaning that when you come to use this coffee from the fridge, you're actually using stale and part brewed coffee. Used coffee produces a cup that will be bitter and over-extracted.
Freshly roasted coffee is always a winner, but when storing coffee, use the bag it comes in whilst trying to keep it away from oxygen, moisture and light. These three factors accelerate the process of staling. Once opened and resealed, carefully squeeze as much air from the bag. The ziplock and valve on the bag will stop oxygen from entering the package.
Once this is done, store in a dry, dark and cool place (most cupboards will do).
We also recommend using whole beans as much as possible and grind these as close to brewing as possible.