I was contacted by a recruiter due to my performance in Google Code Jam. After a few calls and verifying internal references, I was able to skip the phone screen process. My onsite interview was scheduled a month out.

Before the onsite, the recruiter sent information on what to prepare for. This was helpful, but in my opinion, it was overkill.

I would say most of the interview focuses on flexible problem-solving using standard algorithms and data structures, and coding your solution in clean and efficient code.