Job candidates make a lot of mistakes in interviews. That's bad—at least for a person hoping to get hired—but what's much worse is when you, as the interviewer, make one of the following mistakes:
1. Mistake nervousness or shyness for a lack of ability.
Some people just don't interview well. They're nervous or shy and don't make a great impression. An awkward interview does not mean a candidate can't do the job, though: Great communication skills in no way signals expertise.
When candidates seem nervous or uncomfortable, give them the benefit of the initial doubt. Help them relax. You're a leader and your job is to get the best from people—even people you haven't hired yet. You might just uncover a diamond in the deer-in-the-headlights rough.
And if the people you interview often seem uncomfortable, take a step back and consider your approach. You might be the problem.
2. Fail to go off script.
An interviewer should follow a plan and ask a reasonably specific set of questions, but the best questions are almost always follow-up questions. (Most candidates are prepared for an initial question, but questions that drill deeper are much tougher to fluff.)
Listen to initial answers. Then ask why. Or when. Ask how a project turned out. Ask what made a position hard or made a project difficult.
Not only will you get past the canned responses but you will also learn details—positive and negative—the candidate never planned, or would have thought, to share.
3. Expand on possibilities.
Candidates naturally sell themselves. Interviewers often try to sell the candidate on the job. (That's especially true when you love your company.) Before you know it you've described exciting new projects, enhanced benefit programs, opportunities for promotion due to potential expansions... lots of hopeful stuff that might happen in the future.
The problem is the candidate translates "might" into "will," and you've unwittingly created expectations you may not be able to meet.
Never describe possibilities. Describe typical career paths, for example, but only in a general sense. When you discuss future plans only share details on approved projects or efforts currently underway.
If you can't promise, don't bring it up.
4. Spring the surprise group interview.
Group interviews: Convenient for lazy interviewers, terrifying for job candidates. You rarely get the candidate's best, plus it's easy for the interview team to fall into the group consensus black hole where everyone gravitates towards the same opinion.
Of course if the position requires working predominately within a team, a group interview can provide a feel for the candidate's suitability. Tell the candidates ahead of time so they can prepare.
Otherwise, hold individual sessions. It's only fair, to the candidates and to your business.
5. Take over.
Interviews often turn into monologues... delivered, unfortunately, by the interviewer.
When that happens the candidate will rarely interrupt or try to restore balance to the interview because they want you to like them. Thirty minutes later your hiring decision is based on whether the candidate was a good listener.
Briefly describe the opening. Briefly describe your company. Better yet, make sure the candidate has a good feel for the position and the company before the interview. Explain you'll answer questions at the end. Then dive in.
The conversation should be 90% candidate and 10% you—at most.
6. Turn 10 "okay..."s into one "yes!"
It's easy to check off mental boxes during an interview: experience, okay; qualifications, okay; attitude, okay... and before you realize it a mediocre candidate with no negatives seems like a great candidate.
But do you want to hire the candidate whose qualifications and interview fails to raise any red flags... or do you want to hire the candidate who excels in a number of critical areas?
An absence of negatives is not superlative. Always look for excellence. Feel free to check off mental boxes as an initial sorting tool, but then look for the candidate who not just meets requirements but kills the requirements.
Never settle for good enough. If good enough is all you find, keep looking.
7. Ignore input from casual encounters.
Job candidates give you their best: They're up, engaged, and switched on. But how do they act when not trying to impress you?
What candidates do while waiting in the lobby can indicate a lot. Find out how they treated the receptionist, find out what they did while they waited, ask about any chance encounters with other employers... occasionally you can identify a disconnect between what they show you and what they show the people they're not trying to impress.
A jerk in the lobby is always a jerk on the job.