People in the self-checkout line are terrible. Here's how to make them faster.

This is your life: After a long day of work, you're stuck behind somebody who uses a self-checkout at the grocery store like he's a time traveler from the 1800s.

Self-checkouts are great in theory: They save time, kill awkward small talk, and allow you to purchase incredibly embarrassing items without shame. But nobody ever seems to know how to use them efficiently.

This is a problem worth fixing. So I got in touch with two experts from Duluth, Georgia's NCR, the world's largest self-checkout vendor. The company vends about 70 percent of global self-checkout shipments, so if you're using a self-checkout, it probably came from NCR. The company studies all of it extensively in the field and in its own lab, where researchers watch consumers in a fake grocery to see what works and what doesn't.

My guides were Jennie P. Johnson, a human factors engineer, and Monica Hachem, a retail marketing manager. They offered five basic tips that anyone can use to speed up the self-checkout line:

1) Stop looking for the barcode

This is the most important way to speed up your self-checkout time, by far: Never examine your item for a barcode again. Just run it across the scanner. If it doesn't scan, your hand is covering the barcode or it's facing you, so just flip it and scan again.

"Just pass it over the scanner"

"Just pass it over the scanner," Johnson insists. "The chances that it's going to read on the first pass are extremely high."

This works because each register has a "scan zone" that will search the whole product for a code. Think of it less like a laser hitting the code and more like a field that you pass the product through. NCR even tells cashiers to use the "power slide" — they recommend extending your arm like you're shaking hands with the product.

"We've done a lot of testing in our labs and in the field where we quantify how long these behaviors take," Johnson says. "When a consumer picks up an item and actively hunts for the barcode, they usually spend about 2 or 3 seconds per item." That's a roughly 50 percent increase in total time per item.

So trust the technology. Swipe, don't look. It will work.

2) Don't worry about accidentally scanning an item twice.

This low-angle shot conveys the excitement of using a self-checkout machine. (Boston Globe/Getty Images)

We've all seen it: Somebody examines a barcode, gently moves the item toward the scanner, and then pulls it back as if it might explode. People are paranoid about scanning twice, but you don't need to be — most self-checkout software protects against it.

"The protection against double scan is with our weight-based security," Johnson says. "The scanner is actually disabled until you place the item in the bag. There is also technology built into the scanner — a same-item lockout timer — that normal cashiers will have. If it sees the same barcode within 500 milliseconds, it won't read or report it."

3) Buying produce? Remember your favorite codes.

A banana with the classic PLU. This number should be burned into your banana-loving brain. (Justin Sullivan/Getty Images)

If you've ever been a cashier, you know the significance of #4011. That's the price lookup code (PLU) for bananas, and it's the little number you see on produce stickers. If you get the same produce a lot, it might make sense to memorize the PLUs.

"Cashiers, through their training and experience, start to learn some of the more common produce codes," Johnson says. "A lot of savvy self-checkout users have done it as well."

You'd be right to note that it shouldn't be your job to remember PLUs when you go to the grocery. After all, you can always use the produce lookup tool instead. But memorizing your top codes will get you through the line and home faster.

4) Scan your loyalty card at the beginning, not the end

It's natural to scan your loyalty card at the end, when you have your wallet out to pay. But Johnson recommends you scan it at the beginning instead.

Why? Many self-checkouts feature customization for each user. For example, if you need to look up produce on the self-checkout, the list is customized to your purchase history. It will show your most-purchased produce first and save you some time scrolling through the list.

There are other possible perks, as well. For example, the loyalty card can automatically set your language or email you a receipt. It can even make the self-checkout smarter. "If you're an expert user, you'll never see a prompt," Johnson says. "We call that multi-pathing — we've tried to design the system to handle both expert and novice users."

5) A few more tips for true self-checkout pros

There are a few other things you can do to become a self-checkout pro (and make other shoppers less annoying).

One tactic is to "gamify" your experience. Cashiers are frequently measured by how many items they scan per minute, and you can do it too. The average self-checkout size is six items, and the average transaction time is about 85 seconds — see if you can beat it. Soon, you may have help making your checkout experience into a game: some of NCR's scanners have a "power bar" that lights up as you scan more quickly. Hachem says that for cashiers, "it helps reduce training costs and shows up every time you scan."

Finally, there's one other training tip you can take from the pros. Some cashiers will practice "power slide" scanning by wearing a blindfold. Please consult a manager before attempting this on your next visit to the grocery.

Some obstacles are tough to overcome

Shoppers wait in a long line, despite following all the self-checkout tips. (Brent Lewis/Getty Images)

All those tips should work wherever you shop. But some things are up to the grocery stories, hardware stores, and other retailers that actually sell you your stuff.

For example, you might have trouble knowing when to remove your full bags of groceries, but that's probably more the retailer's fault than the self-checkout's. "The system has been designed to be flexible in terms of removing full bags," Johnson says, "but that's all configured and decided by each retailer. They choose how much independence or flexibility they want to give to the shopper."

The same goes for those delays when you buy alcohol, DVDs, medicine, or other age-restricted items. The best practice, according to Johnson, is for the retailer to let you continue scanning while the cashier makes their way over to check your ID. However, that's all retailer-approved.

And sometimes it's the government that determines self-checkout rules. California, for example, doesn't allow alcohol sales at a self-checkout machine.

Obstacles aside, most of these tips will work wherever you shop. And if you use the self-checkout with confidence, you'll be able to get home quicker.

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