7 surprisingly common interview mistakes that can cost smart people the job

Any of these goofs will send your application to the reject pile.

You're ultra-qualified for the job and super prepared for the interview. You've done your homework, researching both the company and the hiring manager you're about to meet. You're prepared with intelligent questions and great examples of past accomplishments that prove you'd be a great fit for this position.

You may think all systems are go, but there's still a lot that can go wrong, according to career development expert Vicky Oliver, author of 301 Smart Answers to Tough Interview Questions. In fact, she says, research shows that most interviews go south because of social blunders, not poor qualifications.

When you interview, the person you're talking with will extrapolate from your conversation to try and guess what it would be like to have you around every day. Keep that in mind, and be careful to avoid these all-too-easy errors:

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1. Arriving late, even with a good reason.

Yes, there may have been an accident that caused a traffic tie-up, but it might not matter. "Walking in late, even when you have a legitimate excuse, will test your interviewer's patience," Oliver warns. As a practical matter, this means you should plan to be at least a half hour early, and then wait in a nearby caf, park, or even your car until you can show up five minutes before the appointed time.

"Even worse is showing up late and unprepared," she adds. Your only hope is to wow the interviewer with your relevant observations and insightful questions. If you can't do that, you likely won't get the job.

2. Failing to make eye contact or having a weak handshake.

"Much can be determined about a job candidate's character from the initial handshake," Oliver says. "When you have a weak grip, a clammy palm, or won't make eye contact, you imply a lack of confidence and timidity that would make a bad fit in most work environments."

While failure to make eye contact is not necessarily a sign of meekness or dishonesty, most people instinctively perceive it that way. So practice looking the other person in the eye while shaking his or her hand firmly until it becomes second nature. It will serve you well in all sorts of social situations.

Click through for more of the worst body language mistakes to make during an interview:

3. Distinctive clothing.

You may love that novelty tie or those big, unusual earrings, but leave them at home when heading to a job interview. Yes, they'll be memorable--but you want the hiring manager to remember you for your intelligence and personality, not your attire.

"Your professionalism comes across immediately through your choice of interview attire," Oliver adds. Even in a casual workplace, showing up to a job interview in casual clothes may lead the hiring manager to believe you'll be casual about your job. Likewise, if your clothes look like they'd be in place at a party, the interviewer may assume you don't know how to dress for business.

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4. Slouching.

Most of us are guilty of this at least some of the time, but don't let it happen during a job interview. "Body posture conveys a great deal about an applicant's personality," Oliver says. "Slumping signifies lack of confidence, leg swinging equates with nervousness, and arms folded against the chest demonstrate belligerence or arrogance. Pay close attention to the cues communicated through your body posture. Hiring managers will read them accordingly."

5. Talking too much.

If you're anything like me, you tend to rattle on when you're nervous, but that will work against you in a job interview. "Interviewees who pummel the interviewer with questions, prattle on in their answers, or feel compelled to fill any silence with chit-chat will have hiring managers recoiling from their unchecked verbosity," Oliver warns. Right or wrong, the hiring manager is liable to assume you'll be a nonstop chatterbox if you get the job.

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6. Bad grammar or excessively informal speech.

Poor grammar signals poor communication skills to most hiring managers, Oliver explains. "Candidates who use colloquial phrases or are very informal with language can't cut it in the professional world, where written and verbal skills are paramount."

Even worse is profane, derogatory, or otherwise inappropriate language, which, she notes, "shows a lack of sophistication or self-censorship." Make any of these errors and you can expect the interview to end quickly.

7. Unprofessional communication channels.

Your personal email and phone are your own business. Still, Oliver says, if hiring managers see "hotmama" or "partydude" as part of your email address, they may think twice before extending a job offer. The same holds true, she says, if your voicemail message features loud music. "No question, they'll move on to their runner-up candidate and you'll be back to the rsum-submitting stage again."

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