If you have not already known their leadership principles, make sure you prepare 2 to 3 stories related to each principle. Do not trust them when they tell you some principles will not be tested, still, prepare them, you never know. Another way to properly understand their leadership principles is to search some recruiters or former Amazon employees' blogs about leadership principles. They will tell you what's the real meaning behind each of the principles and what they would expect from your answers and make sure you use STAR format. Pro tips, some behavior questions do not just ask for one set of leadership principles, some questions may seem like they are asking you a few different ones, so make sure you prepare a similar story but for different principles, for example, "tell me a time when you have a tight schedule and you failed to deliver" and "tell me a time when you have a tight schedule but you were able to deliver". Similar but they are testing you different principles here.