Congrats to those of you who got invites - that's half the battle!
1. There are generally 3 rounds of interviews, but there will only be two rounds this year (due to scheduling conflicts for interviewers).
2. bring a simple picture - one that just shows your face. neutral background is good, and nothing that shows a lot of skin. The purpose of the picture is purely for the admissions committee to remember a face with the paper applicant.
3. it makes absolutely no difference which round, day or time you decide to interview.