Get there at 8:30 and start filling out the green question form. It takes a considerable amount of time and you want to fill it out properly. Additionally, you are generally called to interview in the order you arrive. You sign in as you arrive. Overall, the day is very organized and time is well spent. But bring something to read, you may have a little down time.
My interviewer was pleasant, warm and enjoyable to talk to. I had a very positive experience during the day from start to finish.