To prepare for interviews, recruits should be ready to demonstrate authentic interest in Google, and the job they are applying for. As an example, they might do some homework on what they love and hate about Google.
Furthermore, Google wants to hear about 'what potential recruits think'. However, authenticity, passion, and interest are not often demonstrated by many people, because they are terrified by the interview situation. Therefore, candidates should take a position on something and ask questions, if they feel that an issue is important to them (it might also be important for Google).