Take some time to review the company website and get familiar with some of their clients. From there it is really about knowing your own story i.e. why you want to work in entertainment/PR? What kind of experience have you had in an out of school that could give you a leg up? What are you passionate about in the entertainment industry? Remember to keep it personable and convey your passion for the job or the industry but remember that it can be a conversation between you and interviewer. Ultimately, I advise that you know your answers to the above and most of the basic interview questions without making it too rehearsed so as to allow them to get to know your personality.