I'm going to admit that there is always going to be that one or two, or three times, where you end up taking something home in a plastic grocery bag, and sooner or later, that uncontrollable mass of plastic bag starts to consume space in your house. You might even have a plastic bag holder, but isn't it FULL by now? Here is a much smaller, tinier method of storage, that my mom will never post into an Instructable, (it's her idea) so I feel it's my responsibility.
Step 1: Flatten Your Plastic Grocery Bag
Step 2: Fold Into a Long Skinny Strip
Fold the bag in half, longwise,
and once more to get a long, skinny strip.
make sure the air inside the bag is smoothed out after every fold, so it's flat!
Step 3: Folding the Bag
Continue folding this triangle until you are at the end of the strip.