A recent ABA Journal printed the advice of a legal recruiter out of New Jersey, remarking that the law student sitting in for an on-campus interview should seek to speak for approximately 80% of the time. The rest of the article gives fairly common interview advice (research the firm you are interviewing for, have all of your materials with you including resume, transcript, and writing sample). The “80/20 Rule” may not be set in stone, but I think is a factor for something else: to make yourself memorable (in a good way) during the interview. And you definitely cannot do that if you don’t contribute enough.
The article is available here.