What's the No. 1 thing you should look for in a new hire?

Two of the most successful living entrepreneurs have the exact same answer to this question: Look for someone who is a good person.

Really, that's it?

Yes, both Richard Branson, founder of Virgin Group, and Elon Musk, founder of Tesla and SpaceX, have admitted hiring someone who is "a good person" is key to their success.

Says Richard Branson: "If you're good with people and you really, genuinely care about people then I'm sure we could find a job for you at Virgin."

Elon Musk similarly affirms this, saying, "I look for a positive attitude and are they easy to work with. Are people gonna like working with them?"

As a CEO myself, this initially seems like conventional wisdom. Of course you're supposed to hire someone who's a "good person." Duh!

Yet despite this, time and time again, we let someone who is not a "good person" slip through. Just the other day, I spoke with a CEO who spent seven months doing damage control because he'd hired one toxic, "bad apple" in his 100-person company.

Like Elon Musk and Richard Branson, how do we hire for someone "being a good person"?

We often mistake politeness or friendliness for signs that someone is a "good person." That's not true. Just because an interviewee laughs at your jokes doesn't mean she'll help out a teammate who's in a tight spot.

To assess a potential hire for humility, honesty, selflessness, and empathy--all defining traits of "good person"--here are four questions to reflect on during the interview process:

1. When talking about an accomplishment, does the job candidate talk only about herself?

When you ask during an interview, "What do you see as your greatest accomplishment?", listen closely to the answer. If the interviewee's answer is only about herself--celebrating her own individual accomplishment of hitting a sales goal or winning an award--she might not be the team player you're looking for. Instead, if she talks about how she helped coach a coworker to success, that's a sign she's thinking of others before herself. And, that's the mentality you should be hiring for.

2. When discussing a mistake made in the past, how big is the mistake that the job candidate is willing to share?

You might ask, "What's a mistake you made in your last job?" during the interview. Pay attention to the answer here. If the job candidate responds with something minuscule, such as making a typo in an email, you'll want to dig deeper. Everyone in their careers has made bigger mistakes than that, and you want to find out how willing this person is to share them. If they're not, then you may have a candidate who is too prideful to divulge a mistake. That's a red flag this person is not a "good person" to work with.

3. When was a time the job candidate gave feedback to her former boss?

Employees who genuinely care about the success of the company are the ones who will be the most honest with you--even if it means putting their own reputation on the line. To assess for this, ask the job candidate about a time she gave feedback to her boss. Does the she have a hard time remembering an instance? Or can she easily recall a moment when she kindly and directly shared constructive feedback? If someone can give meaningful feedback to their boss in a productive manner, that's a "good person" to work alongside.

4. When you ask about a time the job candidate dealt with an upset client, how'd she handle it?

Almost every employee has had to deal with an angry or frustrated customer. How that person talks about that situation reveals a lot about if they're a "good person" to work with. For instance, if the potential new hire mocks the customer or expresses resentment--it's clear this new hire can't connect and empathize with why the client might be reacting this way. On other hand, if the potential new hire expresses care and understanding for the client's situation, even in the face of the client being miffed, you've got a "good person" to work with on your hands.

The next time you're in an interview, take a page out of Elon Musk's and Richard Branson's book: Look to hire someone who is a "good person" and consider these four questions.

I promise it'll help you suss out if someone's a "good person" before it's too late.