The process begins with on campus interviews, which are fairly simple behavioral questions. There are a few basic accounting questions, certainly nothing to worry about but review some transaction accounting questions just in case.
After the on campus interviews and if all goes well, you will go to New Jersey for the "invitational." This was a very cool experience, as they take care of everything, this was a highlight of the interview. On the first day, there is team building and one interview. The interview was all behavioral and directly out of a book. The second day includes an interview, team building, and a case study. The interview is the same as the first, all behavioral. The case study session gave you 90 minutes to read a case, come up with a solution, and create a small presentation that you will give to 2-3 managers. Tip: don't just focus on the financials of the case, it's easy to get sucked into that thinking, rather, think about the whole business itself like marketing, sales, customer service. They are also testing your ability to think on your feet and they will rapid-fire questions at you.
My final thoughts are that the process was very structured and professional, however, there are nearly 50 candidates there and just about every person interviews with someone different, so it would be very difficult to accurately compare the candidates. Also, there was a networking cocktail hour and the leaders of the invitational put WAY too much weight on the importance of it. It should be fun and relaxing, not an additional interview.