Be confident and don't oversell yourself. And google job interview tips.
Be dressed in an appropriate dress for the company and job. Never dress less than a business casual which is a minimum of dress pants, nice shoes (no tennis shoes/skate shoes), a button up shirt or polo, and well groomed.
Know the company a bit. Do research as to what they do, their history, etc. Don't try to force your knowledge on the interviewer, but more base knowledge is always good and gives you a base about the company.