While technical skills like data analysis are often touted as must-haves for young people entering the workforce, Kevin O'Leary says there's something else they should focus on: listening.

"If you're just starting off in your career, the No. 1 attribute you should think about is learning how to listen," the "Money Court" judge and O'Shares ETFs chairman tells CNBC Make It. "Listen to the people around you. Listen to your boss. Listen to your peers. Shut up and listen."

By spending more time listening and less time talking, O'Leary says young employees can take in more information that will ultimately help them advance in their careers.

"Listening to people and understanding what you're doing, why you're doing it and what the rules are gives you tremendous power," he says.

O'Leary says he learned the power of listening from a CEO at one of his companies. She told him that her "trick to success" was to reverse the "general tendency" that he says exists for an individual to spend two thirds of their day talking and one third of their day listening.

"She reversed that ratio," he says. "She listened for two thirds of the day and spoke for a third, and what she learned was she had much more information at her fingertips with which to make decisions."

In addition to listening, O'Leary previously told CNBC Make It that new employees should keep a written record of their progress and make sure that their boss looks good. Focusing on performance is especially important for remote workers who have lost the ability to "schmooze around the water cooler at lunch" with their bosses, he added.

Sign up now: Get smarter about your money and career with our weekly newsletter

Don't miss: Billionaire Ray Dalio: Trying to time the stock market is harder 'than competing in the Olympics'