One of the most common mistakes that Big 4 candidates make is trying to be someone they are not. They may have a picture in their mind of the "typical" Big 4 employee: outgoing, very social, boisterous. They then go out of their way to play up this Type A personality when in reality they are more introverted.
If you are an extroverted individual then, by all means, just be you. However, if you are shy or more reserved, that is OK. Big 4 recruiters are looking for someone who is confident in who they are; someone who is at ease and easy to talk to. The most effective way to display these traits is to stop focusing on being someone else and just be your natural self.
Big 4 Guru