To help you avoid letting bad habits shine through at the worst moments, we asked experts to highlight some of the least professional behaviour you could demonstrate that will almost certainly cost you a job. Here are 15 of their most illuminating answers that cover every step of the interview process - from resume creation to body language.
Having a sloppy resume
Your resume is your first contact with HR or recruiters, explains Rosalinda Oropeza Randall, an etiquette and civility expert and the author of Don't Burp in the Boardroom. Typos, grammar mistakes and formatting issues will land it in the 'no' pile within a few seconds.
"If your resume is sloppy, they will assume you are, too," she says.
Poor grooming and hygiene
Water shortage or not, if there's one occasion you really want to shower for, it's a job interview.
"Do you want people focusing on the musty odor that surrounds you or your brilliant words?" Rosalinda Oropeza Randall asks. "Lack of effort in your appearance can be construed as potentially lacking effort in your work and work area."
Grooming in public
Vicky Oliver, author of 301 Smart Answers to Tough Interview Questions and Bad Bosses, Crazy Coworkers & Other Office Idiots says it's a good idea to pack a small grooming kit for a quick touch-up before an interview. But rather than apply lipstick or brush your hair in the reception area, you should arrive a few minutes before the interview starts, duck into the restroom, and complete your final grooming before the interview.
Dressing too casually
As they say, dress for the job you want, not the job you have.
'Sloppy clothes scream 'I don't care!' and are a surefire way to put off those around you,' Randall says.
And dressing too formally for an interview can tell an employer that you didn't research the company culture and you're not a fit.
Being late (or early)
Frequent tardiness is a common bad habit, but do whatever you can to avoid showing up late to the interview.
It will tell the hiring manager that you are irresponsible, aren't taking this process seriously, and don't respect their time. And this is not the first impression you want to make.
Plan to arrive at least 15 minutes early. If you find yourself running way ahead of schedule, TopResume's career expert, Amanda Augustine suggests killing time by ducking into a coffee shop or walking around the neighbourhood.
Why? Showing up too early isn't great, either. It can be frustrating for the hiring manager, as your early arrival could throw a curveball into their schedule.
Texting while you wait
You might be asked to wait after turning up for an interview, but be careful not to let boredom get the best of you.
Texting while you wait will make you look as if you would rather be elsewhere. Most waiting areas have magazines, Randall says, and if you see a company brochure, even better. Reading that will reflect your interest in the company.
Not doing your homework
"Employers take note of candidates that are educated on the responsibilities of the job opening in question and on the company itself," says Rosemary Haefner, chief human-resources officer for CareerBuilder. "This demonstrates that you made the decision to apply for the job after considering the facts, rather than out of desperation."
Speaking without thinking
This is a terrible habit - and it can be especially detrimental during a job search.
Saying the wrong thing to the receptionist, for instance, can crush your chances of landing a job. Receptionists are often the first set of eyes and ears a company has, and what you say to them may make its way back to hiring managers.
Continually asking the receptionist if she is sure that your interviewer knows you're waiting for her out in the lobby may convey your neuroses, Oliver says. And flip comments like 'Hey, beautiful,' aren't the compliments you may think they are.
Projecting a bad attitude
"If you doubt your abilities or see only the worst possible outcome, your interviewer might pick up on that negative energy," Haefner says.
"Similarly, it's important not to bad-mouth a former boss, coworker, or employee during any stage of the interview process,' she says. 'Even if your former boss or organisation is known for its problems, a job interview is no time to express your anger."
Another bad attitude, arrogance, is often confused with confidence. Walk into the interview with a mix of confidence and humility, smile, and show some enthusiasm, Randall says.
It's understandable to be nervous during an interview, but you want to make sure you give interviewers more to go on than one-word or rushed answers.
Interviews, which generally involve a lot of talking about oneself, can be especially trying for shy people, and the unfortunate reality is that shyness is sometimes misconstrued as insecurity and even incompetence.
Harvard Business School professor Amy Cuddy suggests taking your time to answer a question, which shows that you're taking the other person seriously and conveys a sense of power.
"When someone asks you a question," she said, "trust that they really want you to answer it thoughtfully. So don't even be afraid to pause before you answer it. Reflect; don't jump right in."
"It's rude to interrupt. When you do, it shows others that you don't have any respect, judgment, or patience," Randall says.
While participation can earn you some brownie points, bad timing can wipe those points away.
In a recent CareerBuilder survey, 69 per cent of employers said that catching a candidate lying about something is an instant deal breaker, Haefner says.
"Lying or exaggerating during the hiring process can destroy your chances of ever being hired with that employer," she says. "And because of extensive background checks and references that come into play before an offer is made, it's easier to be caught than you might think."
Being too eager
Asking, "How did I do?" or "Did I get the job?" projects eagerness that bridges on desperation and neediness. It's one thing to be excited about a job prospect, but you don't want to appear too hungry.
What's more, these kinds of questions are just plain awkward, as they put the interviewer on the spot. You'd be better off following up about feedback after you are or aren't offered the job.
Poor body language
"What you say in an interview is as important as how you say it, and bad body language takes away from your words," Haefner says.
In a recent CareerBuilder survey, employers said that some of the biggest body-language mistakes job seekers make include failing to make eye contact, failing to smile, and bad posture.
Nervous habits like jingling your keys, shaking your leg, and scratching your head can also be construed as boredom, Randall says.
"Interviews are highly stressful, even for those doing the interviewing," Oliver says. "Through your body language, try to convey how delighted you are to be given the opportunity to compete for the amazing job."
Not being gracious
According to Business Insider managing editor Jessica Liebman, one of the biggest mistakes you can make when competing for a new job is not saying 'thank you' after an interview.
"Whether we spent 30 minutes meeting in the offices, we Skyped because you're abroad for your junior spring semester, or we did a quick first-round phone interview, you should always follow up later that day or the following day to say thanks and reiterate your interest," Liebman says.
A few things happen when you don't send a thank-you email. The hiring manager assumes you don't want the job. They think you're disorganized and forgot about following up. And there is a much higher chance they will forget about you.
You can find more job interview mistakes to avoid over at Business Insider.