What is the best way to store ground coffee?
The two main issues with ground coffee are:


The coffee losing its aroma. The aroma/flavor of coffee is quite volatile, and will evaporate very easily. The solution to this is an airtight container, with as little head room in it as possible.
The coffee soaking up moisture from the air. This makes the coffee... unpleasant. The best solution I've found (in a hot humid climate) is to put it in the freezer. It is the nature of refrigeration to leech all of the moisture from the freezer compartment.


In summary, the best I've found is a small airtight box in the freezer.