How to tell a colleague you hate their idea without crushing their spirit

(CNN) Your colleague says they have a "brilliant" idea for a project your team is working on, and you are excited to hear about it. But it turns out to be a total dud.

What do you do?

You don't want to crush their spirit, but you also don't want to waste time on an idea that just isn't going to work.

"You have two objectives here: to come up with the best work product you can and to maintain a relationship with the colleague," said Lindsey Pollak, author of "The Remix: How to Lead and Succeed in the Multigenerational Workplace."

The trick is to shut it down gently, while still making your coworker feel valued and respected.

Don't immediately dismiss it

The idea might be terrible, but don't just knock it down and move on.

When someone approaches you with an idea you think misses the mark, try to take more of an exploratory approach, suggested Marie McIntyre, a career coach and author of "Secrets to Winning at Office Politics." That means shutting off the urge to be critical and being more open and receptive to the idea.

"Don't immediately respond with judgment, whether good, bad, workable or not," she added.

Take the time to hear them out and let them explain their thought process on why they think their idea is good.

Keep in mind that some of the biggest successes weren't immediately seen as flashes of brilliance.

Ask the right questions to show the cracks

Asking questions can lead your co-worker to discover the reasons why the idea isn't so great on his own.

Try asking something like: What are the benefits of this? How do you see this playing out? How does this meet the project or client's objective?

"Challenge them," said Jodi Glickman, author of "Great on the Job: What to Say, How to Say It. The Secrets of Getting Ahead."

"You want to ask them questions to get them to the place where you are. You are trying to show there is a disconnect and their idea isn't going to lead to the right outcome."

Asking such probing questions can also help you find any parts of the idea that might actually work.

Explain your concerns

If you are at a loss for words, embrace the power of the word "interesting," recommended McIntyre.

"You can always say anything is interesting," she said.

It's a neutral word that continues the conversation skeptically, but doesn't immediately squash the idea.

It also helps to be clear when expressing your concerns, so the person feels heard. Say the idea is an interesting approach but you have concerns, and then detail those concerns, suggested McIntyre.

"If you have listened and respected their idea and they feel represented they are more likely to listen to your feedback," she said.

However, if you're on a deadline and don't have time to thoroughly explore an idea, you can take a more direct approach, said Pollak. "Tell them you don't think it's going to work, and this is why."

Ask yourself if it's really a bad idea

Sometimes our own preconceived notions or preferences can prevent us from being open to a new idea, so it's important to step back and make sure you're being fair in your assessment.

"Just do a quick check in with yourself or someone you trust," said Pollak.

Getting a second opinion can also help end a standstill.

"If you can't come to an agreement, suggest having someone help to see what you two are missing," said Glickman. "But make sure it's in the vein of getting a second or third opinion as opposed to getting permission."

When you're in charge

If you are the boss and an employee comes to you with a not-so-great idea, you have more power to shut it down -- but you don't want to create an environment where people are afraid to think outside the box or come to you with new ideas.

"Your goal is to encourage the creative and helpful thinking," said McIntyre. "If your response is always to say what might be wrong, even if it's true, you will get a reputation as not a good person to approach with new ideas."

Setting clear objectives and goals with projects helps keep workers on track and provides an outlet when a bad idea comes your way.

Instead of saying the idea is bad, Pollack recommends saying something like: How does that meet the objective or the criteria?

"The objective becomes a third party. It's not you criticizing the idea, it's saying here is the criteria we need, does this meet that?"

But at the end of the day, you are in charge and you are responsible for the work produced by your team and might have to kill an idea.

"Say: I appreciate the time you spent on this, it's been interesting, but I am not sure it would work right now," suggested McIntyre.