I generally take a day or two a month, and go digging. I start at Pandora, or Lastfm, and listen, with a note pad in hand. I list any songs, and artists I like, then list the “you might also like” recommendations.
Then I go to fye, or any sight that lets you listen to a few seconds of the songs, and see if I like the overall feel. I also go to youtube, and search, and pay attention to the recommendations. After a few hours of listening, I usually have a list of a few dozen bands. I can narrrow that down alot, but its a good start.
If Im really bored, Ill cross reference the musicians in the bands I like, and search for any side projects they are doing. And I look for them to list the bands they listen to, and go look for them.