Because of the high number of people applying for any single job and the emphasis on higher applications in recent years, job interviews have become more and more important. Avoiding common mistakes that most interviewees make allows you to stand out from the rest of the pack and show a recruiter that you are a perfect fit for his opening.

Don't Answer with "I Don't Know"

This is the number 1 job interview mistake people make, and the reason why so many companies lose candidates who are actually very qualified.

When the interviewer asks you an on-topic question, you should not be tempted by the foolishness and the "easy way out" of stating "I don't know."

Instead, tell them that you are going to check on an issue, or even if you are just being honest, elaborate to say what you will do to overcome this difficulty.

No interviewer expects you to have the knowledge of Wikipedia, but everybody knows that most of the knowledge in the world is on the internet. You need to show the brains that you will actually go look it up (on Google or ask a friend, or at least you will do something about it). It would be very unprofessional to tell them that you have no idea to answer their question.

In addition to the classic "I don't know" don't, read more interview dos and dont's here.
Important Dos and Don’ts of Answering Interview Questions
Millions of things you can say, or you can stay mute. Mostly, it’s not about what to say but how and when to say it, so we have some pointers for you to consider before you recklessly answer questions during your next interview.

Like in exams, it is better to try in a futile attempt than to leave a question blank and unanswered. In an interview, conjure some kind of reply to buy yourself time to think - it is a far better alternative than to implicitly give up with "I don't know".

It is only reasonable for an interviewer to give you time to respond, so you should want to extend the thinking time as much as possible so you can craft a more wholesome reply.

Tips to Buy More Time in An Interview:

  • "Give me a second. Let me think through it."
  • "What I know about this is [short answer]. I will try to recall from my past experiences; give me some time to recollect."
  • "This question is about a difficult topic. I don't want to say that I don't know, because I do know a little about it, but without much depth. So here's what I know - [short answer] and I can go look up more about later on and I am willing to learn more."
  • "I have some references at home - books and notes from my time in university. Though they are not on-hand with me, I can drop you an email with the details by this evening. If that is okay with you."

In any case, you should have done your homework to research on a company before the interview so you can answer most of the interviewer's questions.

How To Research A Company Before An Interview
Start With a Standard Wikipedia Search | Use Linkedin to Research on Key People & Their Connections | Social Media - Public Updates & News, Customer Sentiment | Corporate Website

Being Unprepared for Hidden Agendas

A hidden agenda is where they ask a lot of questions that they want to know about, but are not necessarily related to the job.

Here are some questions they may ask:

  • Are you single?
  • What is your Instagram or Telegram username?
  • How old are you?
  • What are your hobbies outside work, or back in school?
  • Are you the only child or do you have younger sibilings?
  • What do your parents work as?

These interview questions infringe on your personal space as these questions are unrelated to the work you've applied for.

Here are their hidden intentions:

  • To chase after you, to date you, or start an unsolicited romantic relationship (boyfriend/girlfriend)
  • To view your personal photos on Instagram or Facebook (stalking)
  • To befriend you, your siblings or your parents outside the work setting and recruit them into their personal social network (empower their social circle)
  • To get you to join their club or sell you a product based on your interest (financial gain)

At the onset, the questions can seem to be part of the interview.

Interviewer Bias: What You Should Expect
• What Is Interviewer Bias• Examples• Why Interviewers Have Biased Opinions• Identifying Person & Situational Bias• Considerations• Tips to Reduce Bias

Here are their excuses for asking personal questions:

  • An interviewer can say that he wants to "know you better as a person" and "not just as an employee" (altruistic)
  • "Part of the process" or "required question" (blames on the red tape)
  • The interviewer uses or hints at his position or seniority, e.g. Assistant Director, to ask personal questions (professional status)

I am telling you now, this is rubbish.

When you interview, you are trying to initiate a transaction.

  • You: Sell your service
  • They: Pay for your service

There are no friends at work, they eventually take advantage of you (heard of backstabbing?)

More Than Friends: Why You Need Your Own Social Network
• Value of Large Social Groups at Work• More Allies Than Enemies• Eyes and Ears Everywhere• Happiest People are Connected• Counter Office Gossip and Win• Capture Attention You Want

To best prepare for an interviewer's hidden agendas, knowledge is the first step.

You've gained that knowledge by reading the above and for you to reach this sentence is explicit that you agree with my reasoning. (At least a preliminary agreement)

Here is what you do next when you come face to face with such bullshit.

Countertactics against Personal Questions and Hidden Agendas

  • Divert the topic to something else
  • Stick to the job description & emphasize that his questions are irrelevant
  • Tell the interviewer to drop an email (which won't happen, since he won't shoot himself in his own foot)
  • Smile, nod, and wait until it becomes awkward so he moves on to another question
  • Walkout (only if you can't handle it) and then make a police report against the individual and the company. Also, consider making them go viral for all the wrong reasons on TikTok or Instagram.
What Are The Off Limit Topics for An Interview?
• Age• Religious Affiliation• Marriage, Sexual Orientation or Gender Identity• Disabilities, Medical Information and Health History• Race-based Hiring Practices• Social Security Number / Identity Number

Do Not Voice Your Promotion Expectations

Telling your potential employer that you hope to be promoted to a supervisor in 2 years and become the department manager a year after your first upgrade in your job title is a sure-fire way to show overconfidence.

Being confident and sure of your abilities is no doubt great, since it shows that as an employee your mindset seems to be in the right place. However, expecting your boss to promote you before the time comes (and even before you've been tested "in the field" or, be trained, and thus "battle-ready"), is an over reach you should avoid.

Your career expectations should remain private until you have cleared the initial interview because it give you and the employer to find if there is a good employer-employee fit in the first place. Promotions and future change in responsibilities are a more mature topic that should be left for subsequent conversations.

Are Career Ladder Promotions Automatic?
What is a Career Ladder? | Why do most promotions at work look like that they are automatic promotions? | Will planned promotions deviate? | The Purpose of a Career Ladder | Can I have career progression without promotions? | How to Plan a Career Ladder

Failure to Make Meaningful Conversation

Many people fail in their job interviews because they spend too much time preparing what to say rather than how to engage in a meaningful conversation. The most successful interviewees know how to get the interviewer talking, rather than just themselves. In an interview, you should remain silent most of the time and only speak at the appropriate time, saying things that really contribute.

Less is more.

You could have exhibited this mistake back during the interview session, among other mistakes. These are early signs you may have missed.
Early Signs of a Failed Interview
• Interviewer’s Disinterest• Lack of Progress in Your Job Application• Poor Answers, Low Standards• Wrong Answers• Negative Response• Fatal Errors Made • Nervousness

Purposely Appearing Uninterested or Bored

Trying to play hard to get? This is not dating! Many people doing a job interview have been known to appear uninterested or bored, even though they are really interested in the job. They do this because they want to show that they are not desperate for the job. This can backfire because people will start to think that you're really not interested in the job and might lose interest on their own.

If you bombed your interview this way, you could be doing these other mistakes as well - see the linked article.
Reasons Why You Haven’t Gotten the Job Yet
• You Bombed the Interview• Your Resume Did Not Stick To the Job Requirement• You Did Not Return Calls, Emails or Follow Up After the Interview• Didn’t Show Up• Other Candidates Applied Earlier• •
Maybe you didn't intend to look bored, but you are just tired from low sugar (and haven't had anything to eat yet). Well, you should at least grab a small bite!
Should I Eat Before an Interview?
• No to Full Meals• Snacking, Water and Coffee• Timing When You Eat• Benefits• Dairy, Spicy & Fatty Foods• Eating Comfort Foods• Breakfast in the Morning

Being Rude Without Realising It

Although this is the most obvious of all mistakes, many people still make it. This is because they are not aware of the effect that their attitude has on others. If you are rude, no one will want to work with you if they have any choice in the matter. Always put yourself in a positive light and make sure that you behave as if you were a respectable person holding an important position. The icing on the cake is that if they like you, they will often be much more likely to want to hire you.

Being Unprepared for Q&A

Although preparation for a job interview is frequently discussed, many people preparing for an interview still go unprepared. Being prepared for a job interview means knowing not only what to say but also knowing what questions to ask. To prepare well, you must undergo at least a few mock interviews with a friend or relative, if not with an actual interviewer. During these sessions, ask intelligent questions. Throw at the interviewer questions to make them think you've done you work, and have thought through the position and the company.

Overusing Filler Words like "umm" and "uhh"

Filler words are words that are used when we're trying to figure out what we want to say next. They are often of the nature as if they had been spoken by an unintelligent person. A lot of people use filler words like uhm and uhh, others say like a lot because they feel uncomfortable with silence. Instead of filler words, always try to take the time and be as confident as you can. This will make you feel a lot more comfortable, and be perceived by others as well.

Telling People You're Not Interested Before They've Said No

Many people have been known to do this, but when it happens it is most often because they assume that other people want them to be interviewed. You should always keep an open mind, and at least go through the motions of interviewing. If they most likely will not hire you, they will usually tell you before the interview is finished, but they might offer a counteroffer to your application.

Purposely Appearing Uninterested or Bored

Trying to play hard to get? This is not dating! Many people doing a job interview have been known to appear uninterested or bored, even though they are really interested in the job. They do this because they want to show that they are not desperate for the job. This can backfire because people will start to think that you're really not interested in the job and might lose interest on their own.

How to Build Rapport With Your Interviewer
Ways to Build Rapport With Your Interviewer | Benefits | When Should You Keep A Professional Distance? | Exceptions | What Happens If You Don’t Build Rapport With Your Interviewer?

Speaking Too Much During an Interview

When people would say far too much during an interview, their words have no substance. This happens because they are so nervous that they talk too much, and the interviewer just sits there and could just tell them to go on, watching them put on a show for their own entertainment. What an easy way to look like a fool and a laughing stock at the same time. If you do end up doing this, the best thing you can do is to apologize for talking too much.

Being Overly Defensive in Your Answers

Defending your answers in an interview can actually be worse than not defending them. This is because if you are asked a question, it means one of two things: either the interviewer wants to know more about what you've just said, or they don't believe it. In the case of the former, answering "Why?" will make you look as if you're trying to justify something that might not even need justification (the interviewers just want more information on why you did what you did). In the latter, answering "Why?" will make you look guarded and suspicious.

Either way, being overly defensive can be a big turn-off for recruiters. They assume that they'll be able to get all the information they need just by asking, so there is no need to say more than what's asked of you.

Being Too Impressed by the Company

Some people get blinded by an employers' reputation, or maybe they can't help but follow the hype of a successful company. Don't get too star-struck by talking about how amazing the job is going to be. The most important thing is to make sure you can do the job.

Leverage on the skills you bring to the table; highlight the strengths you've previously presented in your resume.
Resume Help: List of Skills and Talents
• General Skills & Talents• Job Specific Skills & Talents• How to Find More Skills and Talents to Add to Resume• How to Further Elaborate on Each Skill Pointer

Arriving Late or Excessively Early

By arriving late you are actually showing off to the interviewer that you don't have enough time in your schedule for this interview and maybe you just decided to fill in the time with this interview. By excessively arriving early, you are showing off that you have nothing to do but sit around waiting for the interview.

Put it right by arriving around ten minutes before, so you're not rushed or even sweaty when you go in for your interview. Appear organized and in control.

Be prepared with items you need to bring.
What to Bring to a College or University Interview?
• Paperwork & Preparing Copies• What’s in Your Interview Bag?• Pen• Powerbank• Backup Cash• Waterbottle• Invitation Letter• Smile• Script with Talking Points• Bringing & Storing Originals

Wearing Clothes that Don't Reflect your Image as a Suitable Candidate

In many ways the way a person looks is what their image is to others. This means that how you look reflects how someone thinks of you and that they will make assumptions about your personality based on how you look. For example, a person wearing a business suit and tie will be deemed more responsible than someone wearing ripped jeans with dirty shoes. Some people believe that this is the most important thing in an interview - your image is their impression of you.

Read more about how to dress and interview attire here.
Tie or no tie: Male grooming guide for every kind of interview
Be formal and there you have a good impression. Be too formal and awkwardness sets in. Trying hard to fit into the interview setting? Sure - here’s how you square up your situation.