To maintain the freshness and crispness of popcorn, keep it in a glass jar. Make sure that this jar has an air-tight lid, as one does not want any oxygen hitting the popcorn. This creates a vacuum-fresh seal, which allows the popcorn to snap when someone eats it.
To find large glass jars, one can go to a local garage sale or thrift shop. These are usually very affordable and sold in bulk so that the consumer can store large quantities of popcorn. Run the jars through the dishwasher after people have finished eating the popcorn to eliminate grease and residue.