The only advice I can give is the following...
At the end of the interview, the interviewer usually asks if you have any questions. Try to have a list of 3-4 questions that you would like to ask. Obviously, try to stay away from questions concerning salary. This basically tells the employer that you are serious, and are interested in their company.
Also, you are going to want to look up on the history of the company, this also shows them that you care.
Good luck on your interviews!