Barry Drexler trains his clients for one of the most important moments of their entire lives. No, he's not an Olympic coach. He's an expert interview coach.

Drexler has trained hundreds of job candidates, helping them boost their interview skills so they can land their dream jobs. Here's one question he says you should avoid at all costs.

Never, ever ask about the company's stance on work-life balance, he told CNBC's Make It. "Companies talk the talk about having a great work-life balance," Drexler says. "At the end of the day, they want work out of you. It's just talk."

Seems counterintuitive, right? Work-life balance appears to be all the rage. From remote working days to unlimited PTO, companies try to attract top talent with the lure of flexibility.

But that doesn't mean you should be the first to bring up PTO days or overtime in the interview process. Drexler says touching on the topic of work-life balance could communicate the wrong thing to your potential employer -- that you're not 100 percent dedicated to your work. And that what you care most about it cutting out as early as possible so you can get back to your personal life.

Still, learning about a company's approach to work-life balance is a valid concern. If you're expected to work weekends and stay until 9 p.m., this might not be the right environment for you. (Of course, it depends on where you are in your career and the position you're going for.)

Instead, try tossing out a few subtle questions that can reveal what work-life balance at this company is really like.

  • Can you tell me about the company culture?

  • What sort of leadership style does the CEO have?

  • What's one of your favorite things about working here?

They may bring up the topic of work-life balance themselves by boasting that everyone leaves at 5 p.m. Question answered.

If not, there are other ways to read between the lines that may clue you into a poor work-life balance culture. For example, does the hiring manager talk up their in-office beer keg? Not necessarily a great perk. Translation: You're expected to stay here after hours and socialize with your coworkers instead of going home after work.

Learning about the CEO's leadership style can also provide insight into the top-down approach to work. Would you be expected to leave a family trip to attend to a work-related crisis?

And if the hiring manager seems lukewarm on the company himself and provides lackluster responses to why they like working there, your question is pretty much answered. ​