There are varying number of interviews in different colleges. I personally had to undergo a total of 6 rounds-
a) Written - wherein they tested our command over English. The test though not very difficult, will gauge your grasp over grammar.
b) Group Discussion- a group of 6- 7 candidates are expected to debate on 2- 3 topics. Here I believe the key is to put across one's view without coming across as too dominating. Being balanced and constantly engaged always seems to work.
c) First round (interview) - The first round for me was extremely basic and lots of fun. As I was been interviewed for Online Sales Operations (now Global Marketing Solutions), the interviewer asked me questions pertaining to my favorite ad, my thoughts on online advertising etc. It was a very easy interview and was basically to understand if I was aware of the online platform.
d) Second Round - The second round was largely around scrutinizing my resume and later questions pertaining to my future plans. I was honest about when I wanted to pursue my Masters, later got to know that they were looking forward to such honest answers. (Guess lying about you wanting with the company forever, esp if you're an undergrad, won't work :) )
e) The next two round were via Skype and phone. Both of the interviewers were there to gauge one's analytical skills.