1. Being late. Arriving late to a job interview is often an instant deal-breaker. Hiring managers assume that you're on your best behavior while interviewing, so if you're late, they'll assume you'll be unreliable once on the job. Always allow more time than you'll need to get to your interview so that you have a buffer in case something goes wrong.
2. Being unprepared. Asking questions about the company that could have been answered with some basic research or not being familiar with the job description tells the employer that you didn't bother to do your homework.
3. Not showing enthusiasm. A job candidate who seems lackluster or unenthusiastic about the job prospect will almost certainly become an employee who isn't engaged with the work. Employers want candidates who seem committed and excited, so don't hesitate to articulate your interest in the job.
4. Being rude to the receptionist. Don't just be on your best behavior with your interviewer; make sure that you're polite to everyone you encounter. Many interviewers will ask the receptionist what they think of you. If you were rude or arrogant, that's usually a deal-breaker.
5. Sounding bitter. Job searching is tough, especially in this market, but if you let an extended period of unemployment make you bitter, then you'll turn off potential employers. It's nearly impossible to hide bitterness if you feel it, so it's crucial to find ways to have a more positive outlook.
6. Not giving specific examples in response to questions. If you claim that you excel at problem-solving or that you're an innovative genius and then aren't able to give specific examples, interviewers aren't going to believe you. Make sure to come to the interview prepared with specific examples from your past that show how you've used your skills at work.
7. Claiming you have no weaknesses. You might as well wear a sign saying, "I'm not being straightforward with you." If an employer asks you about your weaker areas and you can't or won't respond with a realistic assessment of areas where you could improve, you'll appear to be lacking in insight and self-awareness. You'll also make it impossible to have a real discussion about your potential fitness for the job. A good hiring manager genuinely cares about ensuring you'll excel at the job, and having an honest discussion of your fit is a crucial part of that.
8. Answering your cell phone in the middle of the interview. If you forget to turn your phone off and it rings, that's forgivable, but answering it isn't. If your phone rings mid-interview, look mortified and apologize profusely--and then turn it off.
9. Sharing inappropriately. Resist the impulse to talk about how much you hated your old company, or the fact that you dated your boss, or your family's medical problems. Employers want to know that you understand professional boundaries and have a sense of discretion.
10. Lying about anything. However much you might wish that you could change the facts about why you left your last job or say that you finished your degree when you really didn't, lying in a hiring process is an instant deal-breaker. Employers want to hire candidates with integrity, not people who show they're willing to lie. And while you might think you won't get caught, you never know whom your employer might know who knows the truth.