I'll answer as well:

I mainly listen to what's in my current library, using shuffle. When I want to discover new music, I typically look at artists of songs I currently like, and see If I like any of their other works.

Ignoring artists and songs in my current library: I mainly discover music from media I consume, such as games, movies, TV and web videos. If I like a song, I'll look it up, and add it to a playlist based on a category (mainly genre). If a song has a album, I may look into the album as well.