It’s been well-documented that we feel busier than ever. So, how do you keep track of what you need to do and when you need to do it? If you’re like most people, you make a list: From high-tech apps to the classic pen and paper, to-do lists remain one of the world’s most popular productivity hacks. In fact, one survey revealed that nearly two-thirds of professionals use to-do lists to stay on top of their tasks.

But not all to-do lists are created equal—and some can even make us less effective if they aren’t set up the right way. That’s why for this Cup of Calm, we’ve compiled the five best science-backed strategies for creating—and completing—an efficient and effective to-do list:

  1. Divide and Conquer

Organization experts say that if you really want to optimize your to-do list, you’ll need more than one. Here’s a useful analogy: When you file important papers, you don’t toss everything into the same folder; you divide them into relevant groups (in an ideal world, at least). You should handle your to-do’s the same way, creating separate lists for work tasks, personal tasks, longer-term goals, and so on.

  1. Limit Your Lists

It’s important to be intentional about what you include in each to-do list, because—thanks to a phenomenon known as choice overload—our brains can only process so many options at a time without being overwhelmed. By studying brain scans, researchers at CalTech were actually able to determine that the ideal number of choices is between 8 and 15. If your lists are longer than that, try clustering similar items by location or function. For instance, if you have to mail a package at the post office and the post office is near the drugstore where you’re filling a prescription later that day, group those two tasks together into one chore.

  1. Think Ahead

Robert C. Pozen, author of Extreme Productivity: Boost Your Results, Reduce Your Hours, suggests spending a few minutes at the end of each day prioritizing your tasks for tomorrow. If you have a freshly prioritized list waiting for you when you start your day, he says, you can hit the ground running without wasting any of your super-charged early-morning time figuring out where to begin.

  1. Estimate the Time Per Task

Include an estimate for how long you think it will take to complete each task on your list. This will help you make realistic decisions about how much you can fit into your day, and as an added bonus, can make difficult tasks feel less intimidating: When you add a time estimate to a tough task, you can shift your focus from what that task entails to how quickly it will be over.

  1. Take Breaks

This tip is less about hacking your list and more about optimizing your own efficiency. Numerous studies have shown that taking time for breaks throughout your day will keep you happier, more focused, and more productive, whether you’re in a corner office or a cubicle.

In fact, scheduling breaks is CEO-approved. AJ Agrawal, CEO of Alumnify, says he likes to compare to-do lists to running sprints: “You work as hard as you can to get to the finish line, then you stop and take a break.” Then you knuckle down for the next set of tasks.

“Either you’re taking care of business, or you’re taking a break,” he says. “Somewhere in the middle is a place you never want to be.”

Over the last 10 years, Janet Ungless has developed a comprehensive expertise in health and well-being as a writer and editor. With a particular focus on sleep, meditation, and wellness, Janet has worked with a host of digital platforms to help consumers live healthier, happier lives. Find her on Twitter @jungless.