Tesla and SpaceX have pretty bold ambitions, as far as companies go: to power the entire world by battery, and to get mankind to Mars, respectively. To keep those goals on track, Elon Musk has to hire some of the most talented people around.

The entrepreneur has developed some pretty distinct hiring practices over the years. Even if your company 's objective isn't to populate another planet, you can channel his tactics for finding the best candidates. Here's how.

1. Interview everyone yourself.

SpaceX is now a 5,000-person company, which would make personally screening every candidate nearly impossible, but Musk interviewed every candidate himself until fairly recently. Generally, the best candidates get a call with a team manager, and then the best of the best must pass through Musk himself. "That's a lot of interviews," he has said.

2. Ask them about a problem they solved.

In interviews, Musk asks candidates specific questions about the problems they solved in previous roles to determine whether they were actually the one who found the solution, as opposed to merely being a member of the team that did so. "If someone was really the person who solved it," Musk said, "they'll be able to answer on multiple levels. They'll be able to get down to the brass tacks. And, if they weren't, they'll get stuck. And then you can say, 'Oh, this person was not really the person who solved it.' Because anyone who struggled hard with a problem never forgets it."

3. Make them solve problems in the interview.

Candidates on Glassdoor have reported being asked engineering and physics riddles in their interviews. Here's one: You're sitting in a canoe floating in a pool with a brick in your lap. You drop the brick overboard. What happens to the pool's water level? Answer: It falls, since the brick was displacing the amount of water equal to its weight while it was in the boat; now it's displacing an amount of water equal to its volume. (Engineers are smart.)

That said, the questions should be relevant to the skills they'll need on the job. "I'm not necessarily looking for someone who has brilliant analytical ability if their job is going to be assembling hardware," Musk said.

4. Don't worry about degrees.

Musk doesn't require his candidates to have college degrees--or even high school diplomas. His thinking: Some of the world's best innovators have accomplished great things without graduating. Musk has pointed out that Bill Gates, Steve Jobs, and Google co-founder Larry Page all lack college degrees. "If you had a chance to hire them," he has said, "of course, that'd be a good idea."

5. Don't settle for anything less than the best candidate.

That goes for any position, from top managers on down. Former SpaceX talent director Dolly Singh said that Musk used to tell her to find the single best person on the planet for any given job, no matter the role. When SpaceX built a yogurt stand in its headquarters, Musk instructed her, "Go to Pinkberry and find me the employee of the month."

6. Seek the right mindset.

Being exceptionally talented is important, but Musk also looks for candidates with a positive attitude. He also considers whether co-workers would like working with them--what he refers to as a strict "no-assholes policy."

"It's very important to like the people you work with," he's said, "otherwise your job is going to be quite miserable."