You've bought the suit...you've polished the resume...now do the research.
Employers expect you to have done your homework before even the preliminary interview. And even if they didn't, it's something you need to do for yourself. Research not only will help you answer the perennial questions "Why do you want to work at organization X?" and "Why should organization Z hire you?," it can help you decide if the job is the right fit for you. This guide suggests places to find both basic and in-depth information about the organizations and individuals with whom you interview.