Having a great interview is often to crucial to getting into a school or getting a job or internship. Be prepared for anything!
Look the part. If you are applying for a desk job, wear what you would wear to work. For a more casual position, it’s ok to look more casual, but generally it’s better to look overdressed than underdressed. Short skirts, overly high heels, flashy makeup, pale jeans, and anything really tacky or dated is generally a no.
Be over-prepared rather than under-prepared. Bring not only a resume, but recommendation letters if you have them and writing samples.
Make sure you have considered you answers to popular interview questions like why are you good for this job? Why do you want this position? Why did you quit your last job? Describe yourself in 3 words, what is the last book you read? etc.
Interviewers like to ask if you have a question for them. Be careful with this, especially if it is your prospective boss, but be a little more inventive or up-front if it is only a college alumni. Don’t ever say no.
Don’t commit major faux-pas like asking how long lunch break is or when you can start taking vacations. Additionally, don’t insult former bosses or coworkers, as this will give you a bad image right off the bat.
Shake hands and always be polite and professional. And don’t shake like a limp fish. Be firm but not like you are having a strength contest. Avoid “like” and “um.” Look your interviewer in the eye and don’t be afraid to smile.
Don’t fidget, be sarcastic or self-deprecating. The interviewer is not your friend, so don’t slouch. In addition, no lying. Say you don’t know if you don’t know, don’t make something up!
Bring up experiences or stories that show why you would be good for the job or how you represent the values of the company. By Shamrockcon, eHow Member 
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