If you are going as a walk-in, be prepared to face more than a thousand people who come for the same reason as you did.
The first round was a group discussion round, wherein the HR called around 15-20 candidates in a conference sort room and asked each one of us to speak about our past work experience or on any topic of our choice. 4 were selected in this round out of the 15-20, based on communication skills and confidence. Believe me, those eliminated in this round were who HARDLY spoke anything at all, you will clear this round even if you rate your speaking skills as 5/10! The poor HR prodded and pushed the candidates to speak at least a few lines so she could judge which processes to place them in, but in vain, eventually leading to elimination of those who couldn't speak up. The HR then said i could apply for whichever position I wanted (TRMS, Transport, Seller support, Customer service) and the other 3 selected could apply for Seller support or Customer service. (This was completely based on the fluency and command over the language, and showing confidence and will to go further).
Since I opted for Transaction Risk Management Systems, I was to go through 2 Versant rounds. The first was computer based in which I was tested based on IQ, English skills, how I would react to certain situations, determining if assumptions were made or not made in the given situations, how the conclusion of certain situations would be according to my opinion. (Let me warn you, this round needs LOTS and LOTS of patience! it is a 45 minute round, requiring you to rack your brains tightly on the given topics and think around them. A few guys got up and left within 10minutes of the start of the test - I hadn't even completed a quarter of my test by then, haha)
It was announced that I had cleared that round and I was handed the instructions for the second Voice versant test (those who weren't selected were given the option of going into Transport voice, customer service or seller support). The 2nd Voice Versant round was completely voice and telephone based. I was given a separate cabin and a telephone and there was a robot on the other end of the call who kept giving instructions on what to do/say/repeat next. I was required to speak in a few sentences into the phone, tell 2 short stories of 30 seconds each, voice my opinion on 2 situations, rephrase sentences and paragraphs. You can make a few mistakes don't worry, the robot keeps shooting questions at you back to back so don't get very nervous about it. Keep your calm and answer confidently.
After telling me I was selected in this round as well, they told me to go back and wait for a call from them next week for the final rounds.
The last rounds comprised of 2, in the first one the Amazon employee (who was in TRMS himself) asked me about what I knew about Amazon, of online shopping, about risks in Ecommerce, how I would handle those risks, how would I determine if the buyer/seller was a fraud, how would I deal with fraudulent buyers/sellers. I pretty much answered everything confidently and correctly to the extent that he asked me if I had done a PhD in online shopping. :D
The second and final round was the HR round wherein she asked me general questions related to why I wanted to get into Amazon, why would I stay committed to Amazon for a long period of time, what my strengths were, how would I decide a success strategy, would I be comfortable working in shifts and over time.
Answer everything in a positive manner and you will be selected.
The people who weren't selected in this final round were asked to try for the Transport round the next day. Maybe those who wouldn't be selected even in that would've been asked to appear for the Seller Support or customer service roles.
All in all, I would suggest rack your brains around Amazon, Ecommerce and fraudulent activities that take place and show them (WITH CONFIDENCE) that you will be committed for a long period of time, and future at Amazon is yours.