When you're conducting a job interview, you probably ask a few of the most common behavioral interview questions. You may, like these CEOs, you ask one or two unusual interview questions.  You may ask a question designed to reveal what the candidate has really accomplished.

And surely you ask at least one of the 27 most common interview questions.

That's great...but if you stop there, that can also be a problem. 

Most interview questions focus on the past: what the candidate has experienced, has learned, has accomplished...but what about the future? What about what the employee will do for you?

Ultimately, that's what matters. Where hiring is concerned, the past is interesting. The future is what truly matters.

That's why there is one question you probably don't ask, but absolutely should:

"What will you accomplish in the first 90 days that will make the biggest difference to our bottom line?"

First things first: Employees are investments, and every employee should generate a positive return on his or her salary. (Why else would you have them on the payroll?) Great employees know that.

In every job, some activities make a bigger difference than others. Great employees know that, too. 

Say the opening is in HR. You need your HR staff to fill job openings, but what you really want is for HR to find the right candidates for your organization. The result is better overall productivity, lower training costs, higher retention rates...all of which positively impact your bottom line.

Or say the opening is in service. You need your service techs to perform effective repairs, but what you really want is for those techs to identify ways to solve problems, to provide other benefits, and to generate additional sales. (Think service techs aren't in sales? Read this.)

So ask the initial question: "What will you accomplish in the first 90 days that will make the biggest difference to our bottom line?"

Listen to the answer and then ask more questions. Ask how. Ask why. Ask not just about goals but also about plans. After all, a goal without a plan is just a platitude or dream.

When you ask question and then ask simple (and obvious) follow-up questions, you learn several things:

1. You uncover what the candidate really knows about your business.

To answer the question, the candidate has to know enough about your business and your industry to know what truly drives results.

2. You uncover whether the candidate wants the job...or just the job title.

Some candidates seek the position. Maybe because it's the next step on their career ladder, or because it means more money, or because they want to stop being an individual contributor and start working through others...whatever the reason, they want the job title.

Others want the job. They want to do the work, and the title just makes it easier for them to do that work. They want to be a sales director because they want to sell more. They want to be an engineering manager because they want to design and build more products. 

A candidate who wants the title will focus on what they've done in the past. A candidate who wants the job will tell you how their past will allow them to accomplish the things they plan to achieve in the future.

3. You uncover whether the candidate intends to make an immediate impact.

Great candidates want to hit the ground running. They don't want to spend weeks or months "getting to know the organization."

They want to make a difference. Right away.

Which is what you want, too.

4. You uncover more about the candidate's cultural fit.

Every organization is different, and so are the key qualities of its outstanding employees.

Maybe your best employees work longer hours. Maybe creativity is more important than following best practices. Maybe constantly landing new customers in new markets is more important than building long-term customer relationships. Maybe your best employees spend the same amount of time educating an entry-level customer as they do a high-end enthusiast.

Finding out how candidates plan to impact your bottom line helps you determine if they will not only fit, but have the potential to be an outstanding employee.

Or maybe provide a work ethic, a perspective, or an attribute your organization does not have--but desperately needs.

Try it. Ask the next candidate you interview how they will impact your bottom line. 

You may be surprised by how quickly a candidate you thought was great turns out not to be...and how a candidate you might have overlooked will immediately rise to the top.