As you probably already know, it is important to do research into the company. Knowing about key people at the company, their products and services, locations, competitors and some current events or news related to the industry. However it is also important that you dress for the interview. Even if from your research you know that the company has a casual work environment, dressing up will send the message that you are serious about your career and the position you are applying for. Being neat, clean and professional is important in making the first impression a good one.