First contact was during an on-campus recruiting event. Some time after, the firm hosted a relaxed social at a local bar near campus. This was an excellent opportunity to stand out and network.
Next came the on-campus interview. The night before the interviews, HR and several firm employees treated the interviewees to nice dinner. This was another great opportunity to stand out and make a positive impression, and it also helped to relieve the jitters and stressors of the formal interview to follow.
Lastly came the office visit. They put you up in a nice hotel, and take you out to a formal dinner the night before. Again, another excellent opportunity to make a positive impression and network. The next day was the office visit. First breakfast, then we were broken into groups to tour the office. The visit was very relaxed and centered around the firm's culture and the actual internship experience. After the office tour we went bowling- yet another chance to network and make a positive impression. The dinner the night before was arguably the interview and was likely the most important part of the entire visit.
Overall: In the end, I felt that they were recruiting and trying to impress me, as opposed to me interviewing and trying to impress them.
Common theme: You have several opportunities to make yourself known. A social, two dinners, a breakfast, and an event (bowling for me). Make the most of it! It's up to you to get noticed.
Advice: the only "formal" interview was the on-campus one- which dictates whether you are extended the office visit. Other than that, the firm likes to see how you interact with people and how you conduct yourself in formal and informal settings.