Promoting a blog is like promoting a site so here we go: 1. SEO 2. PPC 3. Social Bookmarking Sites & Social Networks 4. Article Marketing / Press Releases 5. Guest Blogging 6. Various spam (just kidding or maybe not) etc. etc. Come on don't be lazy and use Google
I like to write related articles, then submit them to article directories and plug them at social sites. Posting comments on other blogs is something I also try to work into my regular routine.