Interviewing potential new employees is obviously a critical step in hiring.  It's also hard and, in our experience, frequently not executed as well as it could be. With that in mind, here a few tips for improving your interviewing process:

1. Prepare an interview script - most questions are not tied to a specific skill or knowledge. Prepare a script  addressing the specific requirements of the position.
2. Ask the same questions - the same questions are frequently not asked of each candidate, which causes serious comparison and reliability issues.
3. Weight the questions - interview questions are usually not "weighted" or prioritized, so minor questions receive the same weight in the final rating as the most important questions are treated the same as the least important.
4. Use a scoring sheet -- a scoring sheet can ensure that interviewees are rated consistently on the same factors. Final decisions are frequently made based on memory. A scoring sheet forces the interviewers to make their decisions based on predetermined factors.
5. Agree in advance on good answers -- interviewers usually ask questions without first determining what a strong or weak answer is. As a result, the same answer will be evaluated  differently by different interviewers.
6. Think about the future -- most interviews and all behavioral interviews focus on the past. Many interviewers fail to ask candidates about the future and how they will deal with upcoming problems.
7. Review the interview - after each interview, take time to record your thoughts and impressions.  After interviewing multiple people and time passes, it is easy to forget an individual person.