8 Costly Mistakes to Avoid When Interviewing a Job CandidateSave money and time by identifying great applicants the first time around.

To be a great leader you must be a great interviewer, since the quality of your organization depends on your ability to find and hire the right people.

As a professional speaker and consultant, I travel around the country conducting leadership development programs. I continue to be shocked by how many leaders are bad at interviewing and therefore aren't getting the best results for their organizations. It's an expensive mistake -- bad hiring mistakes cost companies millions of dollars each year.

To avoid this pitfall, here are eight deadly sins to avoid when interviewing a job candidate.

1. You don't know what you're looking for in a candidate.

Before you start the interview process, it's important to decide what qualities you are looking for in a candidate. This criteria can generally be divided into three categories: competency, culture and experience. Make sure to craft questions that will help you determine an applicant's ability, cultural fit and previous work history instead of open-ended questions that aren't relevant.

2. You ask illegal questions.

Oftentimes, the leaders I work with are shocked to find out that many of the questions they routinely use are actually illegal to ask during an interview. By law, when interviewing a candidate you can not ask about race, creed, country of origin or religion. I often see job postings that ask at least one question prohibited by federal law.

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3.You have no previous interviewing experience.

Many organizations put leaders in interviewing roles, but haven't taught them effective techniques. Interviewing is both an art and science; most people require training to be able to distinguish between excellent candidates and subpar ones with excellent interview skills.

4.You accept the first answer without digging any deeper.

Many leaders will ask candidates question and accept their answers at face value. For example, when asked to give an example of a workplace accomplishment they are proud of, an interviewee may say "I'm very proud of the fact that I won the Edge Leadership Award." A bad interviewer responds by saying "congratulations that's really great!" In contrast, a great interviewer will want to know the specific accomplishments that helped the candidate win, along with more information about the award itself, including how many people receive it each year.

5.You always believe a candidate's answers.

Many leaders are too trusting when interviewing a candidate. People in interviews often stretch the truth, massage the truth or, let's face it, blatantly deceive. Don't blindly accept a candidate's answers. Instead, ask follow-up questions in an effort to determine whether they are lying. You don't have to be accusatory -- this can be done in a professional, diplomatic and friendly way.

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6.You don't require that candidates are interviewed multiple times by multiple people.

To loosely paraphrase Abraham Lincoln, "you can fool some of the people some of the time…" The point is that if you have multiple people interview a candidate multiple times, it's very difficult for a candidate to fool everyone. The other advantage of having multiple interview is each person will have a different experience with the candidate, and learn new things about him or her.

7.You don't ask candidates to prove their skillsets.

For example, if a leader is interviewing someone for customer service position, at some point they candidate should demonstrate his or her skills by taking a fake customer service call. It is perfectly appropriate to test applicants on their listed skillsets, through role play, take-home tests or scenario-based case studies.

8.You talk too much.

In interview is a chance for a leader to get to know the candidate. I've always believed that an interview should follow the 80/20 rule, which means the leader should talk 20 percent of the time and the candidate should talk 80 percent of the time. If the goal is to learn as much as possible about the interviewee, don't waste time with chit chat about yourself.

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