You can have the perfect resume and a compelling cover letter and show up for the job interview ready to impress, but get ready to forgo the job offer if you make one of these stumbles.
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 seeming familiar with the job description tells the employer that you didn't bother to do your homework.