Editor’s note: Managing human beings is one of the toughest jobs you’ll ever face, especially as your team grows. We spoke with six founders about what works (and what doesn't).

Good mentors help you question your own thoughts, think in new ways, and raise your expectations. At Box, we have both formal and informal mentorship. It's so important in a fast-growing company, where a lot of the learning has to be done almost through osmosis. Your employees need to see what other people are doing in their jobs and to be inquisitive. So we have "people partners"--there's one in each department--and a lot of what they do is help people make sure they are getting what they want out of their job.

We recently decided that for the long-term health and success of our company, we want to be sure that 50 percent of our manager positions are filled internally. Hiring from the outside is not a sustainable way to grow. The only way to do this is to invest in your team.

The third sales rep we hired at Box was in 2008. He was about 26 at the time and a natural leader. So anytime there was an inflection point in the company, we got him involved. We made him our second employee on the ground when we opened a European headquarters. We paired him with a very experienced senior VP of sales. So, at his second job out of college, this man quickly rose through the ranks at headquarters, brought his talent to a new region, and benefited from mentorship by a senior person. When he came back to the U.S., we put him in charge of our East Coast enterprise sales team. That's the kind of environment that helps employees thrive.