I’ve been in the IT staffing industry for 15 years, all with Robert Half Technology. In that time, I have seen just about all the interview mistakes that can be made.

Some of these mistakes are minor “style” issues, while others are certain to stop a job offer dead in its tracks. With that said, here are five interview mistakes that I have found to be the most off-putting to the interviewer and can eliminate a perfectly qualified candidate from consideration:

1. Getting off on the wrong foot

As we know, people size you up in the first few seconds of meeting you. A bad first impression is almost impossible to unwind. I have personally interviewed candidates who kept their sunglasses on during an interview, but just pushed them back on top of their head. I have interviewed job applicants who have not only kept their cell phone out during an interview, but actually looked at it periodically.

I’ve interviewed candidates who put little effort into preparing their attire for a professional interview. It’s not about wearing a designer suit, but the little things like wrinkled shirts, scuffed shoes, etc. The lack of attention to small details in an interview can send a message that indicates you’ll be that same kind of employee.

2. Lack of interview preparation

I’ve conducted dozens of interviews over the years where the candidate knows very little about the company, the job or the interviewer. As an interviewer, it gives you immediate pause for concern wondering just how interested this candidate is in the job or the company. If they have not even done some basic research to know who and what they are interviewing for, how interested could they really be?

When you’re interviewing for a job, research the company you’re applying to, as well as the person you’re interviewing with. Be informed so that you can demonstrate your genuine interest. You'll send a message that this is important to you and you have done your due diligence before you walked in the door.

3. Bad timing

Being compensated fairly is important in every job. However, broaching this topic with the interviewer early in an interview can be viewed as bad form. On many occasions I have seen candidates bring up money in the interview before we have even talked about the job in much detail.

Make sure the job is a good fit first. Is this a job you can be successful at? Will you enjoy the role? Is the company a good cultural fit for you? Once you have answered these questions “yes,” then it’s more appropriate to make sure the compensation aligns with your expectations and your research on what the job should pay.

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However, let the interviewer initiate the topic. If you can sense that the interview is approaching the end and compensation has not been discussed, it’s ok to say something like, “I’m really interested in this job and believe it’s one I can be very successful at. I look forward to the next step in the interview process. As I continue to research the company and this role, could you provide me with an idea of the compensation range so that I have a full picture of the opportunity?”

4. Not asking for the job

I’ve seen countless interviews with clients end with the client saying to me that they felt the candidate was very qualified for the job, but they just did not get the sense that he or she wanted the job, or was very excited about it.

Don’t walk out of the interview assuming the interviewer knows how you feel about the job. Don’t assume that just because you’re interviewing for a position that your interest in it is presumed. Again, if you want the job and are confident you can be successful in the role, say something like, “This appears to me a great fit for me and I would really like to have this position and work at your company.”

5. Poor follow up

When the interview is complete, your job as a candidate is not finished. Many candidates sit back and wait to hear about the results of the interview.

Go on the offensive and send a thank-you email or, even better, a hand-written card. Continue to do your research on the company, the job and the interviewer, and send follow-up messages of congratulations on the company’s growth or an interviewer’s promotion. This will send a message of continued interest in the company and your future opportunities with them.

There are many more points I could make around common interview mistakes, but these are five that I have found particularly damaging. If you’re a job seeker, avoiding these can increase your odds of landing the job you want.

This post has been updated to reflect more current information.