1. Showing off
Despite what you might see on The Apprentice, employers are rarely impressed by outrageous claims or displays of ego.
Make sure all your bragging is justified, says Philip Oldham. "The sort of personality that has done everything everyone else has, and has a story about it, is generally out for glory and doesn't put any effort into the job to achieve it."
According to Quora poster Yishan Wong, whose answer recieved almost 2,000 upvotes, "Showing off is a gamble: if you pull it off, good for you. If not, expect no sympathy."
2. Failing to do your homework
In today's information age, there is absolutely no excuse for knowing nothing about the company you are applying to work for. "This includes at a minimum doing your research on what it is and does, but also having given thought to where it's going and how you would contribute," says Jack Lion Heart.
Wong adds: "For popular consumer internet companies, not having created an account or tried out the product even minimally before coming to interview shows you don't do your homework."
"I've conducted so many interviews where I've asked, 'So what do you think of X?' and the candidate has said, 'I've been meaning to try it'," says serial interviewer Jonathan Lane. "Doesn't help to read the textbook after you've written the exam, folks."
3. Making up answers
Inflating your expertise is a quick way to alienate your interviewer. If you don't know the answer to a question, it's better to be up front about it.
"When asked a question they don't know the answer to, a lot of people try to guess, or try to bullsh*t the interviewer, or start going through facts they know that don't really answer the question," says Jadin Attar. "Don't do that. Just state clearly that you don't know.
"A good interviewer will take that as an opportunity. Maybe if given a related piece of information, you will be able to learn the answer on your own. In many cases, that will demonstrate something about your understanding of the topic beyond what you've read and what your experience has exposed you to. It can demonstrate the ease with which you can learn new information and how you connect concepts."
4. Forgetting your manners
"I once had a candidate who was respectful to all his male interviewers and totally rude to all his female interviewers," says Wong. Equally, directing all your answers to the most important person in the room instead of to the person who asked the question is disrespectful.
Swearing and crass comments are also no-nos. "Making jokes is high risk, low reward, even for the ones that land," claims Amanda Henry. "Especially avoid self-deprecating jokes, or jokes that are designed to 'bro out' with the panel. I'm interviewing potential employees, not potential friends. We can joke around later."
5. Asking no questions
"I have always found it fascinating that so many [interview candidates] never ask me anything," says Pieter D Roussouw. "A job interview not only enables the potential employer to assess your skills and suitability but it also enables the interviewee to assess if this company is in fact a good employer, compatible with your needs."
"At least ask something about what you'll actually be doing and who you'll be doing it with," says Henry. "Job postings very rarely give a sense of what an actual day in the job will feel like."
6. Apologising unnecessarily
This is the quickest way to undermine yourself in front of an employer, according to Steven Mason. He warns that "apologising for yourself, for others, for your answers, for your appearance, for anything" could make you look weak. "Apologise if you accidentally elbow someone in the mouth, not because you don't know the answer to a question or you don't agree with them or anything else outside of basic etiquette. Be who you are. Confidently."
7. A bad handshake
"I won't cancel you outright for a bad handshake, but it doesn't do you any favours," says Henry. "They're simple to learn, and prove that you're deliberate and thoughtful about how you present yourself."
That's not the only hand movement that could count against you. According to Jack Lion Hart, "bring hand wave-y" is also off-putting.
8. Failing to explain what you will bring to the party
According to Ed Weinstein, this problem is particularly true of recent graduates. "They use their cover letter to explain what our position can do for them instead of explaining what they can do for us."
9. Moaning about your current employer
"You're not running from somewhere but to somewhere," says Steve Everhard. "No employer wants to feel that you are joining them because it's better than where you are." Instead, show that you are excited by the opportunities the new firm represents.
10. Using 'yes' or 'no' answers
"What is most impressive is the candidate that expounds on the answer, showing how he understands the material," says Brian Feeny.
11. ...Unless the interviewer requires a 'yes' or 'no' answer
"The most common issue I've had when interviewing people is when they ramble on forever," says Tracey Croughwell Saenz. "It's like they're fishing for the right answer but they've got to tell me everything they did in their last job, whether or not it's relevant to the question.
"I really appreciate when a candidate listens to the question, and answers it thoughtfully and concisely. If you need clarification about the question, definitely ask. But don't try to squeeze in every great thing about yourself when you're asked a specific question."
12. Trite or practiced answers
Beware answers that seem too rehearsed - or that you've pulled straight out of an "idiot's guide to interviews"-style manual.
"If I ask a candidate, "What is your biggest weakness?" and they mention something that's actually a skill like "perfectionism" or "working too hard", it lacks insight and is a feeble attempt to impress," says Esha Krishnaswamy.
13. Dressing sloppily
"I interviewed a candidate for a programmer position years ago," says Frederic Gray. "He came into the interview sporting a scraggly beard, unkempt hair, and a dirty T-shirt. I asked him, 'Is this the outfit you expect to wear at work?' He responded that he expected to get paid for performance, not to be a fashion model (or words to that effect).
"I said that if we ever got a job for a programmer that never had to set foot in the office we would certainly call him back in, then dropped his resume in the trash and thanked him for coming in."