I just started listening to different music, not more, but different genres or bands. I realized that I like way more types of music that I knew about. I just kept adding to my collection and just about every chance I get I'm listening to something.
Listen to the radio and try to find something new. Also Youtube and imeem are great ways to discover and explore new music. Instead of using Google, Yahoo or other search engines, use the mp3hunting.com whenever you need to do a search. Lucky for us, there are a few MP3 Search Engine that we can use to access online music!