The hiring process starts with a phone screen. Once you pass it, you are called to Google's headquarters in Mountain View, CA. Here, I had four rounds of interviews with a lunch break in-between. They book your travel tickets and hotel and reimburse your expenditures during your stay. I must say, Google HRs were really helpful in making me understand the entire interview process and offering suggestions.

None of the questions were unexpected. Be sure you know data structures like Maps, Trees, Array/Lists well, and time complexities. They usually ask for the time complexity of your program at the end of the solution you gave.

Also, read about OOD and be thorough. Again, it's Google, so make sure you prepare your best.