You certainly have your favorite music
style and artists, you hear again and again. You learn about new music
from the media - radio, tv, magazines, blogs (Thanks, Chris, for your Tip
Epica 
, I never had found them
myself) - or from recommendations of your friends.
One alternative to come across new music
and artists, which you probably like, is last.fm.
When you enter your favorite artist
into the search field, last.fm searches for him and delivers some information
and songs:
But here I want to recommend you the
"Play similar artists" function:
Further more you can use other users'
tags to discover new artists:
If you click e. g. "symphonic metal",
you can use the so called "Tag Radio" ot the "Track Playlist"
or you browser other similar tags:
Happy "Music surfing" 
