My friend Liz Morley has been having trouble landing a good, stable job. (In our sputtering economy, she's far from alone.) Though she's an excellent writer, she's found herself working as a cashier. There's a modest upside to her situation, though -- for us. She has gained some insights into the world of grocery stores and checkout lines, some of which could save you a lot of money over time.

Here, in her own words, are some regrettable things she's witnessed at her store:

  • People are in too much of a hurry to check receipts for errors. Our display screen allows the customer to follow me as I key in each item, and correct me if I ring up something twice or at the wrong price. Sometimes the sale price does not come up on the scanner. I am not offended at all if someone corrects me. Deli almond butter is dispensed in tubs that say "peanut butter" -- watch for confusing stuff like this.

  • Customers forget what a completely unmarked item is called and how much it costs. A good example is a piece of exotic produce with no four-digit code on a sticker, or a deli item in an unmarked tub. I jot down codes for some of the more popular items, but a mystery item might delay checkout.

  • Money and even cards are dropped on the floor. We collected $2.10 by closing time the other day, just off the floor. And in my lane the other day, I found someone's credit card.

  • People leave behind items or even a whole bag. I blame this on "line guilt." It's easy to feel rushed when you see a line forming behind you. Realize that a smart manager will open another register if a line gets to be too long. It's not a problem to take one's time.

  • Customers hesitate to ask questions in the aisles. The produce folks know more about fruit than cashiers do. The deli guy is more likely to have answers to questions about meat. For some real brain-twisters, the manager might be the best person to consult. It's best to ask your questions before you get stuck in the checkout line, though.

My friend also warned that, "some criminals practice 'shoulder surfing' -- that is, looking over a customer's shoulder in order to collect personal information, such as social security, account and PIN numbers." And curiously, that "Most slips in supermarket aisles are caused not by wet floors but by individual grapes." A final bit of advice: "See what the healthiest-looking customers are buying to eat. You might learn something."

After chatting with Liz, I was eager to see what else I could learn about the world of cashiering. (If you're thinking that an article like this on grocery checkout lines is frivolous, think about it. Odds are, you find yourself in a grocery store frequently. If you change a few behaviors, you might end up saving a lot of money -- just $5 each week amounts to $250 per year, and $2,500 over a decade. That's not chicken feed. Unless you happen to be a chicken farmer, in which case that could well be a lot of chicken feed.)

Here are some additional tidbits about the checkout line:

  • Cindy Brown, at the University of New Brunswick, writes: "The regular day at work consists of working for six hours, repetitively greeting customers, scanning groceries, taking money, thanking the customer. Quite an unchallenging job -- I don't think so. Standing on one's feet for six hours straight is no small feat -- between knee aches, back aches and headaches, six hours can feel like an eternity."

  • A cashier at a Kroger store offered a long list of things to do to not tick off your cashier. A sampling: "Please remember a cashier is not the price-setter, manager, or head/member of another department. Hence, things such as store layout, item prices, and price discrepancies should be brought to the appropriate person's attention and not the cashier's. Please do not place money, coupons, or anything else that's paper-thin on the belt, especially if it's moving. A momentarily distracted cashier may not notice them slip underneath. In the express lane, 12 items means 12 items, not 30. Also, two dozen cans of cat food is not one item, it's 24. Do not assume the cashier is stupid simply because he or she is a cashier. There are some intelligent people behind the registers. They work as cashiers only for one of the following three reasons: they have to due to not being able to find a "real" job, they want to supplement their income, or they simply like doing it. Finally, do not do anything intentionally irritating and try not to be stupid."

  • At the website, I found an interesting discussion on "checkout snobbery," which I confess rang true to me. It involves feelings of smugness and superiority as you scan what the folks in front of you in the checkout line are buying. For example: "Do you find yourself standing in line at the checkout counter looking at what other shoppers are buying and thinking, 'Look at all that money they are wasting'? I catch myself doing it all the time. I do not buy convenience foods or soft drinks or those little juice boxes. I shop in bulk. I pinch every penny until I hear Mr. Lincoln scream, then I let go." And "I see people buy a small amount of name-brand, pre-prepared processed foods, and lots of meat, and other expensive items, and I smirk silently when I hear the cashier give them their total, which is usually in the $40-$100 range. Then the cashier rings up my whole purchase, which is usually raw materials like flour, dried beans, fresh vegetables in season, rice, etc., and I wind up with several bags full of food (which will last me for a week at least) for $20-$30." One person offered this tip: "Another thing that I do is watch to see if someone is really loading up on an item. I will ask them if there is a sale on that item that I missed."

  • My sister reminded me of her own cashiering days at a Wawa convenience store, where she'd always be amazed at the many people who never seemed to compare prices. They would often be able to buy more food or drink for less money, if they just paid attention to prices and sizes. Sometimes the bigger item is on sale and costs less than the smaller item.

  • Perhaps my most interesting discovery was that there's an annual "Best Bagger" competition. (Who knew?)

  • Scratch that -- this just in: In Argentina, cashiers are reportedly being forced to wear diapers, to cut down on bathroom breaks. Jeepers.

What do you think about all this? Share any supermarket tips on our Living Below Your Means discussion board -- or just drop in to see what others are saying. We offer a painless free trial of our vibrant discussion board community.

And by the way, if thinking about money makes your head hurt and you'd like an actual person (a financial pro, no less) to talk to about your situation, look into our TMF Money Advisor. It's a valuable service, featuring independent one-on-one advice from objective financial experts. It can help you make sure you're saving enough and well enough to meet all your needs. To take savings matters into your own hands, visit our Short-term Savings Center, which offers some special rates for Fools.

Selena Maranjian has never been a cashier, but she was a switchboard operator for a summer. Liz Morley welcomes responses to her thoughts. For more about Selena, view her bio and her profile. You might also be interested in these books she has written or co-written: The Motley Fool Money Guide and The Motley Fool Investment Guide for Teens . The Motley Fool is Fools writing for Fools.