Taco Bell CEO Sean Tresvant credits his leadership success, at least partially, to one piece of advice: "Don't try to be a black belt in everything."

Instead, focus on excelling at a single aspect of business — because as you advance your career, you'll only need to be proficient at the rest. "Be a black belt in marketing, and be a brown belt in everything else," Tresvant, who previously held marketing executive roles at Taco Bell, Nike and Sports Illustrated, told LinkedIn's "This is Working" podcast last week.

Tresvant received that advice in January upon becoming CEO of Taco Bell — which is owned by fast food giant Yum! Brands — and it helped him quickly adapt to the job, he said. Instead of believing he has all the answers, he tries to ask the "right questions" to team members who have expertise that he doesn't, he noted.

"I'm not trying to be everything," said Tresvant, 54. "I understand I'm not a CFO, but I have a great CFO who can lead the [financial side of the] business."

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The tactic is a sign of "great leadership," because it helps the people around you develop their own expertise, he added — benefiting both your organization and their careers, a win-win scenario.

"Leaders who try to be everything to everybody, and try to maybe be a little bit too micro, and don't empower their teams to lead — I think that's when teams aren't at their best," said Tresvant. "I try to be a leader who understands what I'm good at, but also understand[s] what other people are good at, and make sure I'm giving them the space to be great."

Admitting when you don't know something

Asking good questions can help you obtain influence and build relationships in the workplace, communication expert Matt Abrahams told CNBC Make It in September. Good questions are concise, advance a conversation and center on a single, focused idea, he said.

Posing strong questions "demonstrates you care, it demonstrates empathy, it demonstrates you're willing to learn and, in some cases, admit you don't know everything," said Abrahams. "Those are all valuable tools and assets to have when you're trying to grow your career or deepen relationships."

There's also a correlation between success and accepting that you don't know everything, leadership expert Charlene Li told LinkedIn's "The Path" podcast last year. People who balance confidence with humility can better learn from failure and bounce back from challenges, helping them improve their performance and make better decisions going forward, she said.

"Because you don't know everything, you can't be expected to have all the answers," Li said. "You can be open to a learner's mindset, and that is absolutely crucial."

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