We tend to be most afraid of what we don't know. Being prepared can take the mystery out of the interview and put you back in control. It starts with having a good understanding about yourself and your abilities. Your plan should be to know what you can do and express it so other people understand your abilities. The next step in being prepared is doing homework about the company to which you are applying.
Interviewers definitely pick up on the applicant's knowledge about the company.
It's a sign of your interest. Even if you only know a few facts, they might help you ask intelligent questions. For example, you might know that the company is in the printing business but not know specific details about their work. This type of question indicates your interest in and willingness to learn about the company. If you can, try to talk to someone already working at the company.