Attach yourself to the front door of a grocery store about an hour before opening. You will be similar in appearance to a barnacled sea cucumber attached to the mossy surface of an undersea rock. You could try puffing out your cheeks while adhering your face to the glass (like annoying little kids do on long car rides). Make eye contact with the employees getting ready to open inside. Drool a little and act jittery - like you can't wait for the store to open.
As soon as a worker opens the door, shout, 'Oh, boy, oh boy!' while sprinting at top speed to the baking isle, and making as much commotion as possible. Emerge triumphantly with a bag of flour, and explain to the checkout person with extreme enthusiasm how you can't believe that you got a bag of flour (they're so hard to find) and how lucky you are. You could also cry tears of joy…