Of  course, everyone has their own opinion, but I will share some of mine as I had the opportunity to be on the other side of the interview table just last week. The candidate had to interview with about 8 people on a single day, and I am sure the process was gruelling for the candidate!

What I found  most striking was the candidate's ability to ask intriguing questions about the work we do since at this point we already know the candidate has  the qualifications to do the job. This was also affirmed by my other colleagues. Be able to ask important questions--not just why, and  how. Demonstrate your thought process in a clear and logical way.  They are not going to be impressed by your saying that you can think through logically--you have to make it apparent.

We were also giving  significant considerations to the personality of the  candidate. That was equally important, I would say. Be cheerful. Smile. Demonstrate that  you are a good fit for the department.