I use a grocery list app on my iPhone religiously (also available for droid). If I realize we are out of storage bags, I add it immediately to my GroceryGadget App. This way I never forget anything at the store and I can make better use of my time.
GroceryGadget allows for you to check things you need at the store and as you check them, it organizes them in categories so you make better use of your time while in the store ie: deli, produce, dairy, frozen foods etc. Once you put an item in your cart, you can check it and it will disappear off of your list. This also helps me to not put extra things in my shopping cart. If it isn't on my list, I am not buying it. I use this app religiously, even when I wasn't eating healthy