It is impossible to read the personality of an interview and we discuss the typical errors candidates make in trying to read too much into the behavior of interviewers: quiet, asking questions, rude, etc. One thing we always caution candidates is to be wary of assuming the friendly person likes them or that the unfriendly person does not like them. Friendliness does not equate to "like" and people display their emotions in very different ways. So, if the interviewer is very friendly, it could go either way.
