1. Not knowing what the company does
This is a no-brainer, but you'd be surprised how many people - even the most senior ones - don't come prepared to answer the question: "What do you know about our company?" No matter how many times you tell an interviewer that you're interested in the position, your lack of due diligence tells the firm: "I couldn't care less." Make sure you learn the basics, like what services they offer, when they were founded, who their founder is and at least one interesting fact about the company.
2. Showing up late
If you're not on time, you might as well consider it game over. Being late tells the interviewer: "My time is more important than your job." Always leave for the interview far in advance - check for traffic or delays if it's during rush hour. At the very least, arrive 10 minutes before schedule. This will also give you time to mentally prepare.
3. Wearing the wrong clothes
Too tight, too clingy, too short, too revealing - men and women both make this mistake. It's also important to do a "culture check" before you pick out your interview outfit. Don't wear a hoodie at an investment bank or a suit at a tech startup. If you dress inappropriately, you're basically saying: "I don't fit here!"
4. Rambling pointlessly
Prepare for the interview by rehearsing concise, to-the-point answers to the usual questions: Tell me about yourself, what are your biggest accomplishments, your strengths and weaknesses, and so on. Record yourself speaking so you can observe your delivery and make adjustments as needed. If you ramble, you're not only telling the interviewer that you didn't prepare, you're also confessing: "I have no idea how I can contribute."
5. Lying, exaggerating, inflating
If you're inauthentic, everything you say about yourself - your experience, your accomplishments, your goals - becomes suspect. Often, interviewers will "level set" by asking a candidate to describe a current project. If there's an obvious mismatch between what you're working on and what you claim is the scope and level of your current job, you're saying: "You can't believe anything I've said."
6. Not staying in your lane
You're not in charge of setting the pace of the interview. Always stay in your lane and go with the flow. It's like driving on the freeway: You can't drive at the speed you want. You need to judge the flow around you. Match the interviewer's pace in the give-and-take of the conversation. Punch the accelerator, and you're broadcasting: "I'm desperate"; ride the brake, and you're saying: "I'm just not up to this job."
7. Being a pest about the next steps
Consistently nagging your interviewer does nothing to solidify in their mind that you'd be a great fit for the job. Instead, it screams of insecurity. If they get multiple emails from you, all the subject lines will basically read as: "I didn't get the last five jobs I interviewed for, so please, please, please hire me!"
8. Playing hard to get
At the same time, don't hold back on your enthusiasm. Many people think that by doing so, the employer will eventually try to convince them to take accept the offer. If you're genuinely interested, say so by explaining why you think you'd be a good fit for the role and organization. If you don't finish strong, the interviewer will conclude: "You don't want the job." And guess what? You won't get it.
A version of this article appears on CNBC.com.
