NEW YORK (MainStreet) — Next time you step into a job interview, you might want to turn off your phone first.

According to a survey of more than 3,000 employers conducted by CareerBuilder, more than three quarters of hiring managers ranked answering a cellphone or texting as one of the most detrimental mistakes a candidate can make during a job interview, making this the most widely agreed-upon interview mistake that can cost you a job.

Other common blunders on the list included dressing inappropriately for the interview and chewing gum. While you might assume that most job hunters know to dress nicely for an interview, the professionals CareerBuilder spoke with said these obvious mistakes are more common than you’d think.

In fact, the hiring managers who took part in the survey recalled specific examples from interviews they had conducted that showed just how unprofessional some candidates can be. One hiring manager noted that a candidate decided to make himself comfortable by taking off his shoes during an interview. Another applicant arrived at an interview wearing a Boy Scout uniform. We’re assuming it wasn’t an interview for a job with the Boy Scouts.

Our favorite mistake mentioned in the survey has to be the following, though: “On the way to the interview, the candidate passed, cut off, and flipped his middle finger at the driver who happened to be the interviewer.” Moral of the story: Your interview begins before you even arrive at the company’s office, so be courteous to everyone you meet while looking and applying for jobs. You just never know.

Of course, there are plenty of less obvious mistakes you can make in an interview, whether it’s broaching a touchy subject or using the wrong body language. Find out how you can ace your next interview with these 10 tips from MainStreet.

Seth Fiegerman is a staff reporter for MainStreet. You can reach him by e-mail at seth.fiegerman@thestreet.com, or follow him on Twitter @sfiegerman.