What did you like to do most when you were a teenager? According to Bill Gates, the answer to this question will tell you what career you should pursue. "The thing you do obsessively between age 13 and 18, that's the thing you have the most chance of being world-class at," he told Charlie Rose in an 2016 interview. So answering that simple, if offbeat, question can give you some clues about where to focus your energies. 

Gates went on to say that there was only one thing he was obsessive about at that age -- writing software. He was so obsessed with it that, in those days of mainframes the size of a football field when time on a computer was a rare and precious thing, he would rise at 5 am to take advantage of an available half hour of computer time. He even hacked into school computers that "we wouldn't generally have been given access to." 

I thought Gates' observation was pretty astute -- I was obsessively writing at that age myself. So I decided to see what some other iconic entrepreneurs were up to during their teenage years.

1. Warren Buffett was investing.

In fact, Gates' pal Warren Buffett was asked what he was doing at that age during an interview with CNBC shortly afterward. "I was pretty interested in investing," he said. In fact, he bought his first shares, in the company now named  Citgo, at age 11. He had many entrepreneurial ventures as a child and teenager as well, and at 14 bought a 40-acre farm that he rented to a tenant farmer.

2. Richard Branson was starting businesses.

Despite being dyslexic and doing poorly in school, Richard Branson was a serial entrepreneur right from the start. He started businesses selling parakeets and Christmas trees, both of which failed. Then at 16, he started a magazine called Student that took off slowly but earned him 50,000 pounds (about $60,000 at today's exchange rates). With that money he was able to start a mail-order record business, undercutting the high prices at London's established record stores. He's been starting companies ever since. The Virgin Group controls more than 400 of them today.

3. Steve Jobs was hanging out with Steve Wozniak and breaking the rules.

Steve Jobs made friends with Apple co-founder Steve Wozniak at 16, when Jobs was still in high school and Wozniak was a college freshman. Jobs loved electronics, but even then he was an iconoclast. He took an electronics course in high school but dropped out when he didn't get along with the teacher (Jobs was long-haired and drawn to the counterculture). According to author Jeffrey S. Young, he decided to create light shows for his high school's avant-garde jazz performances rather than join the electronics club.

At 17, he enrolled in Reed college, but famously dropped out after one semester and simply began sitting in on the classes that struck his fancy. One of these was a calligraphy class. During his famous Stanford commencement speech, Jobs later said that the calligraphy at Reed was particularly beautiful and compelling. At the time, he had no thought that he'd ever use calligraphy for anything -- he dreamed of a career in electronics, after all. But he did two things he would be known for ever after. He followed his instincts without questioning them too much, and he indulged his love of beautiful design. During the speech he said, "If I had never dropped in on that single calligraphy course in college, the Mac would have never had multiple typefaces or proportionally spaced fonts."

What did you do obsess over between the ages of 13 and 18? I realize that much of that time may have been spent on sleep, game-playing, TV-watching, and pursuing the opposite sex. But what were the activities or subjects that made you want to learn more and dig deeper? And are those things part of your career today? If not, maybe they should be.