Today, even a modest grocery store stocks at least two or three types of cocoa powder. Choose the right cocoa powder for the job. I've found that as much as I like dark chocolate, the darker, more exotic cocoa powders—which are fantastic for rolling truffle centers—didn't produce a very good, traditional hot fudge sauce.
Store cocoa tightly wrapped in a cool, dark place. Higher end cocoas typically have a shelf like of just over one year.