How can I promote my blog?

I look at some music blogs and they’re very successful, have a lot of traffic &
they promote a lot of artists. I’m wondering how I can become a part of that?
Maybe making a Myspace, And find unsigned/ underground artists, and ask them if I can promote their music on my blog?
I have some ideas, but not too many. So can you help me do this, make me think of new ideas?