I was referred by a Google employee to this position. A recruiter got back to me in about a week to set up an initial phone screening. Later that week we had the call, it was very brief (about 15 minutes) and she mainly talked a bit for about the role itself (Global Customer Experience, not sales) and asked me about my experience (resume walkthrough type of thing) and one "tell me about a time when.." question. My recruiter was awesome and at the end of this chat she said she wanted to set me up for two more phone interviews with members of the team I would be joining.
Here is where it got interesting. They send you a rather lengthy email describing Google's interview procedures, how to prepare, and a bunch of links to information related to products knowledge (AdWords in this case). So in preparation for this interview I spent about half of my time getting very familiar with the product, and half of my time with general cognitive ability and hypothetical situation prep. This position was a bit of a stretch for my previous experience so I had to work really hard to come up with supporting evidence that I would be a good fit for the role.
The phone interviews were 30 minutes, back-to-back. My first interview was with someone who had been there a few years in a role similar to what I would have been in, and the second interview was with a manager. To start, there were zero product knowledge questions asked (not to say your interview won't have them, just know mine didn't). They were 90% "tell me about a time when.." questions, and 10% hypothetical situations. I did ok in the first interview and recovered with a good explanation as to why I wanted the job. The second interview did not go so well. In particular there was on hypothetical question asked where we were on completely different pages about and it made for an unfortunate vibe to the whole interview.
In the end, as I said my previous experience was a stretch for this role, and my difficulties came from having relatively weak experience examples when they asked "tell me about a time when." I was expecting a lot more product knowledge based on the prep information I was given, and I was also expecting more personality related questions or Googleyness. However, I prepared as best I could and overall it was a really good experience. Naturally a couple days later my recruiter called me with some bad news, but I want to stress how awesome she was and everyone involved (minus one unenthusiastic interviewer) made it a really smooth process. They really do everything they can to help you get the job because A.) they selected YOU because they like you, and B.) it is in their own best interest to have their candidate receive an offer because it looks good on their part. So everyone is on the same page.
The key here is confidence, personality, and preparation. When talking to your recruiter you should sound like there is no other job in the world for you, and just be yourself. When preparing for the phone interviews, do a little product knowledge prep, but really nail down those situational answers. Just google typical interview questions and answer as many of them as you can. You will be asked questions you have not come across so just stay calm, be confident in your response, and ask for a moment to think if you need it (my recruiter highly encouraged this). They will poke and prod at your answers so be prepared to go into detail. Getting caught up in a weak response is the best way to not make it through. They want to see your methodology for problem solving, there is no right answer, just the best one you can come up with.
Again, stay calm, be confident, and prepare those situational responses, I guarantee you will have a better fate than I did. Good luck!