How do you discover new music?

Three main sources for me (aside from randomly hearing songs in various places):

1. Listening to friends' playlists. One friend in particular has a musical taste very similar to mine so I'm always hearing great new songs from her.
2. YouTube video chain. One song leads to another which leads to another--this has helped me find good electronica, especially.
3. Pandora. Not my favorite because often it plays songs I already know or ones I'd rather skip, but it has also helped me find new ones.