He looked down. “I thought…I thought I was getting fired or something.”

Related: 3 reasons to mentor a millennial (or anyone else)

For the next few minutes, I calmed Marcus down—assuring him that he wasn't getting fired. It really was just a lunch to catch up as friends. There were no ulterior motives. It was clear that Marcus didn't trust me enough to think I wouldn't blindside him with an uncomfortable conversation over a casual lunch. To get trust, you must give trust first.

Set the expectations up front

After my lunch with Marcus, I set up what I called the “Principal's Office.” The name was an homage to my days as a teacher. As a kid in school, you knew what it meant when you were called into the principal's office. You also knew what behavior landed you there.

It was a small conference room attached to my office. That's where all my uncomfortable conversations took place, and you knew the reason behind it. This also meant you wouldn't get blindsided by uncomfortable conversations anywhere else—like Marcus thought was happening over lunch.

The Principal's Office is a great tool for internal uncomfortable conversations because it lets you set the expectations up front.

You may not be able to call a client into your Principal's Office, but you can still set the expectations up front. When a client's behavior is cause for an uncomfortable conversation, it shouldn't be a surprise when it takes place.

Uncomfortable conversations with the G.R.O.W. model

We used the G.R.O.W. model for our uncomfortable conversations. That stands for goal, reality, options and finally the call to action: what will you do, and by when? Like the Principal's Office, the concept of a G.R.O.W. meeting is easy to extend to any uncomfortable conversation you're initiating.

It also requires a little preparation up front.

Before having the uncomfortable conversation, take the time to think through the first two letters. What is the goal, and how is the current reality different than the goal?

In a typical G.R.O.W. meeting, the idea is to figure out options for how to take the current reality and hit the goal. Then, with options decided upon, leave the meeting with a commitment from your team about what will be accomplished. Those steps can be tough to do with a client, but that doesn't mean you can't use the same formula. By keeping the G.R.O.W. structure in the back of your mind during the conversation, you'll be able to navigate its direction to a positive result for your company.

At times, it can be helpful to continue through the rest of the G.R.O.W. structure ahead of time. Think through some of the options and what you're willing to do—and what you're not willing to do.