remember that you're interviewing them as much as they're interviewing you-- to see if it's a good match. what's the company's culture, what benefits they offer, their various policies, opportunities for advancement/development, etc. figure out if this is a place where you'd like to spend a third of your life in the coming years.
gather up knowledge about the business beforehand, which not only demonstrates your interest but lets you ask better questions too.
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eta
i did a little search and this turned up quickly-- looks like very reasonable advice
http://career-advice.monster.com/job...q/article.aspx