Hmmm I would recommend you try to be as relaxed as possible (I'd expect the interviewer would help you with this!) and to ensure that you do some solid and relevant research into Accenture - we don't just wont the best profile or candidate to join us, we want them to have as strong an interest in the company as we do. Oh and ask the interviewer plenty of questions! This helps creates a great impression.
Thank you for your feedback!