Dick Costolo doesn't have the air of a man who's barely hanging on. In recent months, a handful of investors and analysts have gone from speculating that Costolo will pay the ultimate price for slowing user growth at Twitter, where he's been CEO since 2010, to demanding that he be fired. It was getting so out of hand that CNBC's Jim Cramer, who'd led the calls for Costolo's head, imposed a moratorium on himself.

Yet Costolo, 51, who founded three digital media companies before joining Twitter, seems unfazed. Maybe that's because the board has vowed its support, and because he has plenty of numbers to marshal in his defense. (Twitter had fewer than 300 employees and $29 million in revenue when Costolo took over; now it employs 3,600 and takes in $1.3 billion a year.) Or maybe it's that worrying about rumors goes against Costolo's devotion to making the best possible use of his time.

No Sidebars, No Sideshows

A typical week for Costolo involves 12 to 15 standing meetings, so he has a few rules for efficiency's sake. First, no canceling. Freeing up that time may be tempting, but it's how small problems become big ones. "I'm the connective tissue between all these groups," he says. "It's important for me to have context for the issues and challenges everyone's dealing with."

Second, no sidebars, ever. Nothing irks Costolo more than someone approaching him in private and saying, "I didn't want to bring this up in front of everyone, but..." That rewards politics over process, he says: "Everyone on my team knows that that's not a valid way to start a conversation with me."

Finally, no PowerPoint. Meetings are for communicating, not wasting time on pretty slides. Instead, Costolo asks managers to type briefings. "If that sounds straight out of the Jeff Bezos playbook, it's because it is," he says. "I totally agree with that."

Building a Clone Army

Shortly after Costolo took over at Twitter, he started asking himself, "What is the highest-leverage use of my time right now?" Focusing on tiny details might earn you a comparison to Steve Jobs, but it's no way to run a large company. "No one will ever hear me say, 'Why don't we pick the color blue?' or 'Why are there four buttons instead of three?' " Costolo says. "I will say, 'This seems like an incremental change when we could be making a bigger bet.' "

One way Costolo concentrates his time is by teaching a quarterly management class that all of Twitter's new managers must attend. The six-hour course includes lessons on setting direction, giving and getting feedback, improving your team, and being yourself. Costolo got the idea from venture capitalist Ben Horowitz, who launched a similar course as CEO of Opsware to prevent its culture from becoming a crazy quilt of other company's practices. "It's one of my favorite things to do," says Costolo, "and you get people walking around not like, 'This is the way we did it over at Google,' but like, 'This is the way Dick wants us to manage at Twitter.

"Sweating Away Distraction"

Among his underlings, Costolo's devotion to his regimen of CrossFit, spinning, and mountain biking inspires awe--and perhaps a little fear. A big believer in the team-building power of group sweating, Costolo and his sales staff attended 6 a.m. SoulCycle classes during the Consumer Electronics Show this year.

For Costolo, physical fitness is a necessity, not an indulgence. "It gives me the energy I need to work the crazy hours we're all working now without becoming completely worn down and unhealthy," he says. But the most valuable benefit of his daily early-morning workouts is what they prevent him from doing: thinking. The mental quietude some seek in meditation, Costolo finds in the gym: "When you're doing some CrossFit workout or sprinting on a bike, you're not thinking about work. You're 100 percent focused on what's happening right now."

The Efficiency of Wandering Around

To keep meetings from eating up his day, Costolo reserves a block of 60 to 90 unstructured minutes in the morning and in the afternoon. He uses the early block, when his mind is fresh and uncluttered, "to make decisions that are hard," he says. In the afternoon, he likes to stroll around Twitter's offices having unplanned encounters. While these conversations may seem aimless, Costolo uses them to make sure the filtered information he hears at meetings reflects on-the-ground reality. "It makes the whole company more productive," he says. "People are less likely to try to snow me in meetings, because they know I'm generally up to speed."


Tuning Out the Noise (and Persuading Others to Do the Same)

In its short time as a public company, Twitter has gone from Wall Street darling to disappointment, with analysts speculating that Costolo will be out of a job if user growth numbers don't improve in the next few months. It's exactly the sort of outside scrutiny founders have in mind when they delay going public as long as possible, but Costolo says his only concern is that it not become a distraction for others. "It doesn't bother me or affect me," he says. "I have a really good sense of what I need to do and what we need to do as a company, and the board and I are on the same page. The tactical thing, then, is you just have to spend time on helping the rest of the company know, 'Don't worry about this. I'm not spending time thinking about it. Don't you spend time worrying about it.' "

If Twitter's rank and file believe him, it's because Costolo warned them this would happen. "I stood up in front of the company on the night of the IPO," he recalls, "and I said, 'Let's celebrate tonight, but just remember that when things are going great, we all know that they aren't as great as everyone says outside the company. And when the time comes that people outside the company are saying things aren't great, we'll know internally that things aren't as crazy as they think.' So now I'm able to go back and say, 'Remember what I told you? It's happening.' "