Editor's Note: What makes a top executive successful? Every month, Janet Gurwitch, a successful executive who built Laura Mercier cosmetics into an innovative industry leader, quizzes a Houston business leader for answers. She kicks off the series with Mark Wallace, president and CEO of Texas Children's Hospital.

Culture Map: What is the most important leadership lesson you have learned?

Mark Wallace: No. 1 is that leadership is everything in life and in business. My favorite leadership maxim is: “Leadership always influences or determines outcomes, not some of the time but all of the time.” Leadership applies to our personal lives as much as it does to our professional lives. Typically, if a person is not providing leadership in their personal life, then they are usually not going to be a very effective leader in their professional life.

CM: What is your leadership style?

MW: I have my own personal definition of leadership, which is: Vision + Structure + People, with people by far being the most important element. My leadership style is also one of high visibility in the organization.

CM: What has surprised you most about having the top job, running your own show?

MW: What is surprising is how hard true leadership really is. It is never easy. When things are going well, it sometimes looks easy, but it never is. I am constantly surprised at how many people in the organization key off of me and what I am saying and doing and focusing on and, from that, they draw conclusions about how well Texas Children’s Hospital is doing. For that reason, when I am making rounds in the organization, I try to always be very upbeat, positive, and interactive with employees, medical staff, and volunteers. I never want them to think that I am tired, pessimistic, or worried about how things are going at the hospital.

CM: If you were hiring a senior executive, reporting directly to you, what kind of questions would you be asking him or her?

MW: No. 1: Tell me what your definition of leadership is. No. 2: Tell me how you pick leaders and give me some examples of how you have developed leaders to grow and to develop.

CM: How do you run a meeting?

MW: On-time, short meetings that have high impact. I like ad hoc, extemporaneous meetings much more than standing meetings. I like to get the meeting started and then sit back and watch and listen as much as possible. I try to make sure that I don’t overpower any meeting simply because of my position as president and CEO. I want everyone who attends the meeting to feel like it is a safe place where they can be honest and transparent in front of the group and especially in front of me.

CM: What is your best career advice?

MW: Work for the best company possible in your field, even if the pay might be less. You will be better off in the long run. Work for Google, Neiman Marcus, Wal-Mart, M.D. Anderson ,or Texas Children’s – great companies.

CM: Anything you have a particularly low tolerance for?

MW: Yes, executives have to be team players. It’s about the team, and it’s not about self. I have fired a lot of executives. I don’t have trouble firing people if they are not a team player. If I have an executive who is trying to compete with other executives at the team’s expense, I have zero tolerance for that and usually excuse them from the organization rather quickly.

CM: How do you judge your own success each year?

MW: I pay a lot of attention to growth and capacity. I am constantly trying to make sure that we have enough employees, medical staff, and in-patient and out-patient facilities so the children and families can easily access Texas Children’s for preventative care, primary care, or something that might be more serious.

Second, I also pay a lot of attention to employee turnover. A high turnover rate in an organization is a proxy for bad leadership.

CM: What are your favorite business books? What are you reading now?

MW: First, The Human Side of Enterprise, by Douglas McGregor; second, Good to Great by Jim Collins. I am currently reading Churchill by Paul Johnson.

CM: What’s your favorite Houston restaurant?

MW: Post Oak Grill.

CM: How do you fit exercise into your busy schedule?

MW: I run early at Memorial Park during the week and on the beach in Galveston on weekends.

CM: How many hours do you sleep?

MW: About five – I don’t use an alarm clock and wake up about 4:00 a.m. I do productive work from 4-6 when all is quiet.

CM: BlackBerry or iPhone?

MW: iPhone.

CM: Are you addicted to it?

MW: No.