How does one hack another's minecraft account?

Ancient Chinese secret

Social engineering - pretending to be Minecraft/Microsoft support and asking them for details
Fake websites - posting a link that asks you to log into your Minecraft account, but sends the login details off to a scammer's email
Also if you reuse the same passwords on insecure sites like forums, then if the user details are slurped by someone and they can see your email and password, then they can try to log into websites with this combination, websites like emails, paypal and minecraft.

You think anybody's stupid enough to tell you?

Take the username and password… Besides you think Microsoft cares about such a low quality game?