Don't forget that the candidate is also interviewing you. In addition to being skilled at asking appropriate questions, ones that will elicit a candidate's strengths and talents, you must be conscious of the impressions you are making as well. Just as the interviewee is selling him- or herself to you and your company, you are basically trying to achieve the same result. Make sure, for example, that you know as much as possible about your company; the interviewee will be looking to you to provide that information.
If you are new to interviewing, be sure to read What Questions Shouldn't I Ask in an Interview? for some good advice on topics that should be avoided at all costs during a job interview.