Expect questions, and come prepared with questions of your own. There is a book entitled similar to "500 questions asked at interviews." Several of the questions I was asked came from that book. Such as "Why should we pick you over others?" and "Would you hire you". I think you can google "interview questions" and practice. Be confident, smile and sit up straight. Look them in the eye and take a second to think about what you have been asked whether you need to or not.
They WILL ask if you have any questions so be ready for this one.