Know who the hell you are and what your strengths are.
Know what your weaknesses are and how you cope to minimize the risk.
It's Ok to not be superman.
remember that the interviewer has more to lose by hiring a goof than you do, so you should understand that the interviewer really has the most at stake. Help them realize that they are not at risk if they decide to hire you.
keep your sense of humor.
Show "belonging" by whatever means you can- (professional position- professional dress; technical position- trappings of your field. etc.)
Look them in the eye. All of them if its a tag team interview- but answer directly to whoever asked the question.
This advice has always gotten me the job and my daughter into a service academy against real long odds.
milo
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People say between two opposed opinions the truth lies in the middle. Not at all! Between them lies the problem, what is unseeable,eternally active life, contemplated in repose. Goethe
These guys can spot a bullsh*t artist a mile away. If you don't know an answer don't try to fumble your way through it. Just say you haven't come across that situation before, spend a few seconds thinking about it and give them an idea of what you might do to resolve the issue or go about to solve the problem. Many times employers are not looking for someone that have the answers but someone who can find the answers. good luck. Be confident in your own abilities. They sometimes employ people that they can easily talk too, that have basic knowledge, because you need to work in a team and they need a team player.
Prepare for "Behavioral"questions. They will present a situation and ask how you would deal with it or have you had such a situation and how did you deal with it etc.