While in my senior year of college, they found my resume online and after setting up a time through email, a person phone interviewed me for 30 minutes. After about 3 business days, they informed me that I would move on to the in-person round at one of their fulfillment centers, or factory centers where each item is processed. I was flown out to the Phoenix location for a 2 day trip with flight, hotel, and food expenses paid. I was supposed to be toured around the fulfillment center with my group, consisting of about 10-15 candidates, but they informed us in advance that they could not do so due to scheduling issues.
At least at the Phoenix center, you are randomly assigned 2 people out of a handful to interview with separately. I interviewed with 2 people separately. The first seemed very rude in particular ways such as not maintaining eye contact throughout my answers and getting distracted my noises in the background. Maybe I wasn't coming up with compelling answers, but she was one of the rudest and seemingly least interested interviewers I've met in my job hunt experience. The second person was a much more pleasant and professional person. The whole experience didn't take more than an hour, with 30 minutes allotted for each interviewer. With regard to my interviewers, it seemed to be the luck of the draw, but I overall had a fun experience getting to travel out to Phoenix and seeing what the factory is like.
It's a lot of behavioral questions for both phone and in-person, so I would just come up with A LOT of situations you can generalize for different questions. They're trying to assess your character and work ethic more so than your actual experience (although it is important to elaborate why HR and why Amazon), so explain specific ways or use numbers to exemplify ways you stood out at previous jobs. Use the STAR method and be very specific. Try your best not to ramble; get to the point. Also be able to relate specific situations to Amazon's Leadership Principles. And one little thing for the in-person round, don't bring anything (including your phone) besides a notepad/padfolio and a pen as security checks you before you enter.