What are the common signs that a graduate interview has been a success or a flop
We try to be meticulously fair during our interviews. We tend to ask similar questions and try to retain a similar demeanor across all of them.

You should know that we don't usually make up our minds during the interview itself. It's not like a job interview. The answers you give will form just one component of our entire impression of you.

And up until the final committee meeting when all of the finalists are put up on the board and ranked against each other, it's very hard to say with specificity who got in and who got rejected. 

p.s. While I try to send my interviewees a quick note by e-mail thanking them for their time, I would be aghast to think that if I forgot to do so that someone would read devastation and gloom into that oversight. Sometimes a missed e-mail is just a missed e-mail.