During the Interview
Put candidates at ease - Interviewing can be stressful, so do your best to help candidates relax. Make sure each candidate is greeted and escorted, if necessary, to the interview location. Start with low-key questions.
Don't judge on first impressions - We've all met them, people who don't make a great first impression but end up being great employees. To make sure you don't overlook these diamonds in the rough, withhold judgment until you've had the chance to thoroughly evaluate a candidate's capabilities and potential.
Tell the candidate a little about the job - While you don't want to dominate the interview time, you should start with a brief summary of the position, including the prime responsibilities, reporting structure, key challenges, and performance criteria. This will help the candidate provide relevant examples and responses.
Don't be afraid to improvise - Plan your questions, but don't feel you must ask only those you've chosen in advance. Be responsive to what the candidate tells you, and build new questions off their answers.
Listen - If you are doing most of the talking during an interview, you will not be able to obtain enough information to distinguish between candidates or to determine a candidate's true competencies. A general guideline is to spend 80% of your time listening and only 20% talking.