Twitter co-founder Jack Dorsey is one of the world's best-known tech billionaires — but one of his secrets to success is a lot simpler than you might think.

Adam Brotman, who spent nearly a decade as Starbucks's chief digital officer and EVP of global retail operations, worked alongside Dorsey during his time at the coffee giant on partnerships with Twitter and Block (formerly Square), where Dorsey is CEO.

Now, Brotman is the CEO of the Seattle-based (and Starbucks-backed) start-up Brightloom, which helps smaller businesses use tools like digital ordering and personalized marketing.

But the years he spent watching and learning from Dorsey continue to have an impact in how Brotman approaches his work.

"I'm a big fan of Jack Dorsey," he tells CNBC Make It. "The biggest lesson I learned from observing and working with him was that he is very clear on what he is doing and why he does it, whether it was at the macro or micro level."

Brotman recalls watching the former Twitter CEO take detailed notes on each conversation during business meetings in Seattle and San Francisco. One time, he decided to ask Dorsey what the notes were for.

"He said, 'I'm sharing these with my whole company,'" Brotman says. "He was incredibly transparent with his team about the different processes and decisions."

Setting clear goals and being a good listener are two of the qualities that have made Dorsey "such an effective leader," Brotman adds, and are qualities that other people should channel in their own work if they want to be successful.

"There's certain patterns you start to notice among incredible leaders in business," Brotman says, naming his uncle Jeff Brotman, the co-founder of Costco, and Howard Schultz, the former CEO of Starbucks, as two other examples.

That note-taking habit, Brotman adds, speaks to Dorsey's broader approach to leading Twitter and Block. "He was always so calm and clear about what he was doing and why, when he knew things, and when he didn't know things," he says. "He was never emotional or erratic – just steady and clear."

Other leadership experts have praised the Missouri native for his quiet leadership style. In a 2019 interview with CNBC, Jeffrey Sonnenfeld, senior associate dean for leadership studies at Yale School of Management, described Dorsey as "a genius who, unlike [Tesla CEO Elon] Musk, doesn't have to throw in your face," and, Sonnenfeld said, unlike WeWork founder Adam Neumann, "doesn't just pretend to be one."

"He truly is brilliant and dedicated – while avoiding the temptations of vanity and flamboyance his own technology offers some with less discipline," Sonnenfeld told CNBC.

Dorsey stepped down as CEO of Twitter in November. Parag Agrawal, the company's former chief technology officer, has taken over the helm.

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