Google describes their process as a series of questions designed to "focus on your general product and strategic insights coupled with your technical and analytical ability." They will send you a lot of links to reading material and youtube videos on how to prep for your interview. (see the bullet list below). In my case, this only helped to sabotage the entire conversation. I ended spending too much time focusing on describing my thought processes (thinking this is what the interviewer would want to hear) rather than my own ideas about a way Google could make money with my proposed solution, and how I personally operate as a Product Manager.
The bottom line is that if you are a kid out of college that has never interviewed anywhere before, then Google's interview tips will be useful to you. In my case, the interviewer seemed immediately uninterested when I tried to structure my answers in the "Google way". And if I asked a clarifying question, it seemed as if he thought I didn't understand what he was asking. And instead of clarifying, he would alter the question. Some of this could have just been his personality as well. Not everyone is a good interviewer.
Interview guidelines + (my tips)
1. brainstorm big, give some deep insights about the industry or trend (a typical question will be an app you use, and what you would do to improve it, what it would take to realize it from a technical standpoint, and how would you measure it's success)
2. ask clarifying questions (only if you need clarification, don't do it just to show them you've watched their interview prep videos)
3. speak in terms of accomplished X by doing Y which led to Z. (i wasn't asked any detailed questions about my background)
4. walk though your thought processes & methodology (if you know what you're talking about, your thought processes & methodology should be obvious to someone who also knows what you're talking about)
5. mention the tradeoffs - caveat your answer and directly addressing potential concerns the interviewer may have with your answer. (again, only if asked)
6. Improve your answers. expect follow up questions, and improve your answers. (ditto)