Step 1. Be prepared. Bring at least two snacks. If using coupons, organize them ahead of time. You'll thank yourself later.
Step 2. Bring reinforcements, at least one extra person whose sole purpose is to push the cart in amusing ways.
Step 3. Locate (scour the whole parking lot if you have to) a cart with the child's car attached so the toddler can "drive". This will buy you a vital fifteen minutes.
Step 4. Work fast to find the items on the list. "Pretend" you have thirty minutes before a bomb is going to go off and you must finish before then.
Step 5. At the 1st sign of toddler's imminent boredom, offer the 1st snack.
Step 6. As soon as the 1st snack is devoured, offer the 2nd snack because a meltdown is not far off now. It's helpful if the 2nd snack is more appealing than the 1st snack.
Step 7. Work even faster.
Step 8. As soon as the toddler shows he's done shopping in not so subtle ways, such as screaming, it's time to go, no matter what's still left on the list.
Step 9. In response to the toddler's pleas to "Walk! Walk!", offer to let him or her give the cashier the coupons, the cash, and/or the credit card. Smile as the cashier comments on how cute this is and resist the urge to explain in great detail how it's actually your amazing foresight and preparations that allow the toddler's cuteness to be evident.
Step 10. Congratulate yourself. You now have food in the house!!! This is no small accomplishment. Then sleep well (provided no said toddlers wake up on the middle of the night from nightmares or just because).