An interview is essentially a two-way exchange of ideas, and the candidate will be interviewing your company just as much as you will be interviewing them. Come up with some standardized questions that all of the interviewers ask the candidate. This helps in two ways: first, it makes sure there is at least some common ground between the different interviewers when it comes time to evaluate the candidate. And second, you will know how truthful (or well-rehearsed) the candidate is in their responses by seeing how much their answers change between interviewers.