First things first, make a plan before you start interviewing. Assuming you have a clear job description and the job posting ready to go, it's time to figure out your interview process - how many rounds of interviewing, which company leaders will be involved, who makes the final decision. Once all stakeholders are clear on what you're looking for in your next hire and how you'll do it, then you can formalize the questions.

Here are the things to consider:

You know you can't ask questions about protected class status, but it can be tricky to know what's legal and what's not. For example:

• You need to know that the employee will reliably show up on time, so you ask if they have proper childcare lined up... but no, you can't ask about marital/family status. 
• You CAN ask if they have any concerns about their ability to make it to work on time.
• The candidate has a fascinating accent, so it's only polite to ask where they're from... nope, that's too close to the issue of citizenship.
• You CAN ask if they're authorized to work in the U.S., or about languages they speak, if it's relevant to the position.
• You know the job is physically demanding, so you ask if they have any medical conditions... but that's not okay, since that's questioning their disability status. 
• You CAN ask specifically if they have any conditions that would keep them from performing the requirements of the job.
• You need someone who can be on-call at all times, so you ask if they go to church on Sundays and can't work then... oh boy, just not okay. 
• You CAN ask if they're available to work weekends, if it's relevant to the job.

You've probably heard that it's better to ask open-ended questions than yes/no questions, and that's true. Getting the applicant to poen up and talk is critical for understanding who they are. So instead of asking a simple question like "Do you get along well with people?" you should get the candidate talking to see how he/she would actually get along with the team or customers. 

A traditional approach is to word these open-ended questions as "Tell me about a time when you..." and then analyze what you hear. We actually don't recommend this tactic, since it can be biased against people who might be great in the role but don't yet have much experience to draw on. Instead, phrase your question as "Imagine you're in such-and-such a situation. What would you do?" The candidate can then demonstrate their approach and tell you how they'll behave at your company, instead of simply explaining what they've done in the past.

When clients come to us for employee management advice, it's rarely about issues with technical skills. Usually it's the soft skills that cause problems - like customer service, problem solving, communication, interpersonal relationships, etc. If you spend your interview focusing solely on the technical skills needed for the job, you may end up hiring an amazing technician who's unable to show up to work on time and can't communicate effectively with homeowners. 

If you only have a small candidate pool to choose from, we recommend you emphasize soft skills above all else. It's a whole lot easier to train an employee in technical skills than to teach them soft skills like responsibility or perseverance. 

Make sure everyone who's involved in the interviewing process gets to weigh in and share potential red flags. It's easy to spot candidates who aren't qualified for the role, but other issues may be more subtle. For example, a candidate who blatantly over-shares about his personal life in the interview might become a major headache down the road if this over-sharing leads to employee (or customer) complaints. Focus on the critical needs for the job, including the soft skills, before making a decision. 

Lastly, remember that you can still have a bad hire, even if you do everything right. The goal is to minimize how often this occurs, and asking the right interview questions gives you the best chance of success.