Be late or excessively early: Although being late for an interview is a surefire way to fail, being too early can have the same effect. Employers don't want you hanging around for 30 minutes making the person at the front desk uncomfortable. It can also make you seem too eager, as though you really have nothing better to do with your time.Open mouth, insert foot: You want to fail an interview in style? Open your mouth and just let it all roll out without regard to how your words might affect your interviewer. Offensive jokes will definitely do the trick.
Sell yourself short: If you walk into an interview not willing to show off your qualifications and why you'd be an asset to the company, what was the point in even going? Except to fail, of course.
Talk about your former boss: Once during an interview I spoke very badly about a former boss. Honestly, he was the devil, so its not like I was telling lies. Although I did end up getting the job, my interviewer kindly pointed out that in future interviews, I should keep my comments about former bosses to myself. She said it was the one thing that made her second guess her decision to hire me.
Keep your cell phone on: Cell phones have become the thorn in the side of many situations. I had a friend who was at a funeral where someone's phone not only rang, but they got up to take the call. If you have your phone on during an interview and it starts ringing away creating a distraction, then you've successfully failed your interview. Don't be surprised if you're asked to leave immediately.
Put yourself on mute: Potential employers want you to be creative, innovative and show them you can think outside the box. Putting your ideas and personality on mute will make you stand out less, and your resume can easily be misplaced.
Tell them you're perfect: Human beings are flawed -- it is fact. No one is perfect, even the ones (especially the ones) who think they are. Telling an interviewer that you've never made mistakes and that you're the true definition of perfection will put you in the liar category. Employers don't like liars.
Repeat your accomplishments: If every accomplishment you've ever had at each of your jobs is the same, you're living proof that what you have to offer is limited and you haven't evolved as a person. Companies want to hire people who evolve and grow.
Royally screw up your thank you note: Misspellings, swears, comments on the interviewer's bad toupee, anything at all that shows a lack of respect and appreciation will land you in the "thanks, but no thanks" pot of applicants.
