How a hacker might trick people giving him their user IDs

Consider how a hacker might trick people giving him their user IDs and passwords to their Amazon.com accounts. What are some of the ways that hacker might accomplish this? What crime can be performed with such information?
Hackers usually trick users into giving them their user IDs by asking them to click on links or download attachments. They can accomplish this by sending a malicious file to the user’s computer. They also pretend to be legitimate sources sending messages to users. They can use such information to commit phishing in cyber-crime.