Every career coach will tell you that preparation is the key to interview success. Few ever talk about the key to interview failure. To understand how to succeed, you need to understand the ways you can fail.

Here’s your study guide to bombing your next interview.

Show up late

Hiring managers, like the rest of us, are short on time and likely have other appointments scheduled after yours. They tend to look favorably on candidates who show that they value their time. Most managers agree that arriving ten minutes early gives you sufficient time to check in with staff without becoming burdensome. When asked about appropriate interview arrival time, one manager flatly stated, “I won’t likely know if you’re early, but I’ll notice if you’re late.”

Dress inappropriately, and don’t even think about brushing your hair

In an online poll of HR professionals, personal hygiene and inappropriate dress stood out as the most egregious offenses of all job candidates. Describing his worst interview experience, an HR manager recounted a particular job candidate who chose to attend his interview shirtless – he didn’t get the job. You don’t have to wear a suit, especially if the company’s culture is informal, but you do need to wear a shirt. In fact, play it safe and stick to business casual attire for your interview.

Be on your worst behavior 

Chewing gum, taking a phone call during the interview, or otherwise interrupting will hurt your chances at connecting with the hiring manager and all but obliterate your chances of securing the job. But small errors can quite literally cost you as well. Calling your interviewer by the wrong name or widely gesturing with your hands won’t make a good first impression. Make sure to get plenty of sleep the night before your interview, and prior to your arrival take some time to review your interview preparation materials and focus your thoughts.

Be Modest 

While not necessarily a deal-breaker, you’re still missing an opportunity to sell the interviewer your best self. Sure, it may come as a little unnatural to present a total stranger your professional accomplishments and strengths, but if you don’t put those convincingly forward, you’re losing out on an opportunity to show how your experience and education make you the best candidate for the job.

Fail to show how you could contribute to the company

Up until your interview, the hiring manager has had a number of candidates give him the same thing – their resumes. The interview is your opportunity to set yourself apart by linking your relevant work experience with what you know about the company. The better you are at conveying your relevance and showing ways in which you could contribute to that company’s current goals and objectives, the better your chances will be of getting a job offer.

Bad-mouth former employers

Even if you feel slighted by your previous employer, it’s best to keep that information to yourself. If you’re asked to give details on your relationship with a previous employer, compose a frank response and keep it respectful.  Most hiring managers can respect the fact that differences arise that may require someone to move on, but they won’t tolerate unprofessional behavior. Use the limited time you have in the interview room wisely by keeping the focus on why you feel you’d be a good fit for this position.

Be argumentative

If the hiring manager presses you for follow up details on an answer you gave, beyond actually just wanting more detail, that might be a signal that she’d like you to rephrase your answer or perhaps give a more relevant example to substantiate your point. Don’t view it as a personal attack. Keep your calm, take a deep breath, and rearticulate your answer in a new way.

Never show your appreciation

Whether it’s the hiring manager or the receptionist who scheduled your interview, do not miss a chance to tell them that you are grateful. Be respectful and show your courtesy by personally thanking the interviewer for inviting you in to discuss your potential contributions at her company. Sending a thank you email or handwritten letter after your interview gives you a chance to reemphasize your gratitude and remind the interviewer just what makes you the best candidate for the open position.

Following this guide to bombing your next job interview will undoubtedly lead you to failure. Without any preparation at all you’ll be sure to fail your next interview with flying colors. On the other hand, taking the appropriate measures to avoid these pitfalls will bolster your changes of career advancement and ensure you’ll never become a hiring manager’s “worst interview candidate”.