Though the busiest drive-thru lines still move relatively fast, you might find yourself at a standstill if someone ahead of you doesn't know how to follow the drive-thru rules. One such unwritten rule you must always follow is knowing what you want or simply pulling up the menu on your phone and deciding before you get to the order station.

There are some other important rules to follow at the drive-thru that will help the process run smoothly. For example, customers should always avoid being too chatty with drive-thru employees and make sure they have their wallets.

Another big drive-thru rule: don't add any additional items to your order once you arrive at the pickup window. This will certainly put a halt to the smooth system most chains have in place and could potentially expose the secrets of fast-food drive-thrus.