I initially applied for an internship in the winter/spring time, and while there are only two rounds, from what I understand, they are the same first two rounds you receive in the full time process. The first round is mainly to gauge your interest in Accenture. This for me was a pretty easy conversation going over my resume, after which the interviewer left about 15 minutes just for questions. This is mainly to see that you've done your homework and are truly interested and know what your getting into.
The second round for me was held over phone, and this is a behavioral interview. This is the most grueling interview in the process. The interviewer will ask you a question, and then dive into the intricacies of your answer for a while. The main point of this interview is to see what meaningful work you have done, and whether you've done enough to be a part of the company. Be sure to use relevant examples that answer both the question as well as show some of the skills that Accenture is looking for.
After the second round interview, I was informed that while I would not be offered an internship, I had done well enough to earn a final round interview in the fall when full time recruiting resumed. I kept in touch fairly frequently with my second round interviewer from that time till the end of the process. Anybody you meet at Accenture for the most part will be willing to help, so long as you are proactive enough to ask.
I finally got an invitation for the final round interview in the fall. From what I have heard, and from my experience, if you get to this round, then so long as you don't stray from what you have been doing so far, your chances are pretty good of landing the job. All candidates will be paired with a buddy, who's there to answer whatever questions and concerns you might have. First there was a dinner for all the candidates who had made it this far in the process. This was an opportunity to meet several Accenture employees. The goal of this dinner was to inform you more about what it's like as an employee at Accenture, to answer whatever questions you might have, and to just get to know you a little better. The actual interview was about 3 hours. First is a presentation about the company, the various disciplines, practices, and the benefits, compensation, etc. Have some questions to ask during this presentation. Then are two back to back interviews with executives. My first one was very conversational, and was fairly easy. The second one was a little bit more structured, but still nowhere near the second round. Both of these interviews are mainly designed to see if your interests aligns with Accenture, and whether you are a good fit for the company.
From what I understand, after the interview, they will almost always imedeately make a decision for whether they want to hire you or not. If they decide they do, then they will take your location preferences, skills, and interests, and try and find the best match in the best discipline for you. For me, I got a call about a week after the final interview and received an offer.