In preparation for an interview, come ready to discuss your portfolio at length as well as your design process and what design software you are familiar with. Graphic design positions can be very specific to the company so make sure you brush up on the company's current design style and are ready to explain how your style and experience will mesh.
My answer here is the response I received after I asked a question.
When I asked about what were the greatest positives in the department, the interviewer said that everyone was young and energetic. Then she put her hand over her mouth and said, "Whoops!"! The proficiency ?s were very easy; but the interview itself was emotionally difficult.