It happens to the best of us. You run into the grocery store for a few items, just to get in and get out. But when you hit the checkout lines, then you have to make a choice. And so often, you pick a line that doubles your trip.

Line expert and professor Richard Larson estimated that Americans spend 37 billion hours a year waiting in lines. Christopher Mele conducted a study for The New York Times with some counter-intuitive advice on how to limit that. You especially want to keep the psychology behind lines in mind (pages 9 and 15).

1. Choose the fullest carts

According to Mele, the shortest line with fullest carts actually moves faster. Mathematician Dan Meyer explained that human interaction has a lot to do with it. “Every person requires a fixed amount of time to say hello, pay, say goodbye, and clear out of the lane,” Meyer said.

Next: Use the following elementary school math problem to figure it out.

2. Do the math to hack the line

Each interaction between a cashier and a customer takes about 41 seconds per person, Meyer explained. It also takes about 3 seconds to ring up each item. Therefore, one person with 100 items will take an average of almost 6 minutes to process. If you get in a line with four people who each have 20 items, it will take an average of nearly 7 minutes.

Next: Navigating the store differently can also help.

3. Veer to the left

Robert Samuel founded Same Ole Line Dudes, a New York-based service that will stand in line for you. The line expert said most people tend to veer to the right, when shopping. By bucking that trend, you might also pick better lines. Try turning toward the left when facing the row of lines, and see if those seem shorter.

Next: The speed of the cashier can also affect your wait time.

4. Choose female cashiers

“This may seem sexist, but I prefer female cashiers,” Samuel also said. “In my experience, they seem to be the most expedient at register transactions and processing.” While that obviously does not hold true across the board, you might want to watch the cashiers for a second. Do some just move faster than others? Taking a moment to observe could also save you time.

Next: The following tendency can eat up time, too.

5. Watch out for talkers

Psychology professor A. J. Marsden suggested avoiding talkative cashiers. If the cashier strikes up a conversation with every customer, that can tack on serious time. But if the chatty Cathy has fewer customers, that line might also move more quickly. Use your best judgement, in that case.

Next: The following grocery store advice might seem obvious, but it also bears mentioning.

6. Younger shoppers move faster

Older people will also take longer, if only because they might move more slowly. They might also have difficulties with other parts of the grocery shopping process, such as using new machines or technologies. That largely applies to customers, but older cashiers can move slightly more slowly, too. Try to pick lines with younger people, to shave off valuable seconds.

Next: Watch what your fellow shoppers have in their carts.

7. Variety takes longer

Take a look at the types of items your fellow shoppers have in their carts. Larson explained that several of the same item take less time to scan than a large variety. In addition, produce or other items that cannot scan also take longer. You might want to get in line behind someone with six bottles of soda, for example, rather than a cart with a range of produce.

Next: The following method can save you time at the grocery store, but only in certain circumstances.

8. Use self-checkout for easy orders

If you have no irregular items, Meyer said the self-service checkout can work well for you. Some purchases, however, do not work as well for self-checkout. That includes produce, other items without barcodes, and especially bulky orders. Large orders also don’t lend themselves to self-service at the grocery store.

Next: The following type of line can also move faster.

9. Choose a single line leading to multiple cashiers

A serpentine line, or a single line that leads to multiple cashiers, tends to move faster. Think about lines in airports or banks, where the person at the front goes to the next available cashier. We can point to psychology for the reason these lines work better.

Getting into a single line also provides a sense of psychological relief, according to supply chain expert Julie Niederhoff. That’s because customers don’t have to decide on a line. Subsequently, they don’t second-guess their line choice.

Next: The following store layout can also affect how its lines work.

10. Keep your sight lines clear

If you get in a line and can’t see the end of it, you might have a long wait ahead of you. A new study found that lines with obstructed views move more slowly. That happens because cashiers can’t see where the line ends, meaning they have less incentive to work more quickly.

If people can see how their speed affects the wait, they also work faster. Choose cashiers with clear sight lines, for a faster trip.

Next: If you bring a friend, you can also hack the system.

11. Use the buddy system

Use the buddy system at the express lanes to get through a larger order faster. If you bring a friend when shopping — which can otherwise slow down your trip — you can split your order into two smaller ones. That means you can use the shorter express lines. Just make sure you also don’t slow down to gab during your trip!

Next: The way you load up the belt matters, too.

12. Line up your items for easy scanning

You probably already know to leave your eggs and delicate items to the back of the belt, so they end up on top. Turning your items toward the cashier can save time, too. If possible, make sure all barcodes face the cashier, or at least the same direction. That expedites the scanning process.

Next: You also might not wait in line quite as long as you think.

13. A lot depends on your attitude

Research has found that, on average, people overestimate how long they wait in line by a whopping 36%. Customers pay more attention to the length of the line than how fast it moves, explained professors Ziv Carmon and Daniel Kahneman. Given a choice between a slow-moving short line and a fast-moving long one, people will often opt for the short line. Do you do this, too?

Next: You can also make the time go by faster using this trick.

14. Chat up your fellow customers

Waits seem shorter when you have something to entertain yourself. Norton recommends talking to someone else in line or reading the magazines at the checkout counter, to make it go by faster. If you do find yourself in a long line, take heart.

“Try to lose the idea that you are cursed,” he added. “If you remembered the times when it actually went smoothly, you would probably realize that it evens out in the long run.”

Next: When you get right down to it, lines also have one big thing in common.

15. In the end, it all comes down to human behavior

Real cashiers don’t behave like the scientific models, which the Scientific American explains makes all of this research tricky. Unlike those modeled in labs, people work at different paces depending on the task, incentives, and how much feedback they get. That means your cashiers can behave unpredictably, as well.

The bottom line? Sometimes you’ll end up in a longer, slower line. Other times, you’ll strike it perfectly. A lot of it comes down to human error and yes, just dumb luck.

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