It's not the main things, instead the small ones that you tend to fail to notice that can set you back an employment at an interview. The clerk or the secretary you were being mean to on your way in, the janitor at the door; you will never know which one of them could decide to neglect passing your information along.
Don't stutter or reach. If you don't have the answer to the question, be clear and state that you are not quite sure. Make sure that you think about what you are about to say. People have botched job interviews for much less.
You need to be familiar with the nature of business that the company that has invited you for a job interview is into. You should also have a clue how they are structured. They could ask you question along those lines and you want to be able to answer them. In a company that takes their employees seriously, they listen when you speak to them, even at a job interview. So do not hesitate to say a thing or two about yourself if the opportunity comes. You might get the chance to improve matters even for other employees that way.
Your outfit at your job interview has got to look the part of what you are aspiring for. For instance, you cannot go in for a bank job interview looking like a car jerker. There's no way you'll be getting that job that way, and you know it. Just think about this, your personal appearance says a lot about your work ethics.
If you make a habit of being rude, put that away when going in for a job interview. Sometimes the interviewer could be someone with delicate sensibility. If they don't like you on a personal level, there might be nothing else you can do to clinch the job, and you know it. Please, try not to be too annoying.