I think the most important principle is targeting. If you run a blog, post/comment on blogs, forums, etc. There is no end all solution, it all depends on your niche. I research my niche, try to find out how people are going to find my content. If I'm selling an article, I submit to article directories, etc. This should always be an important part of your niche research. Otherwise, you may end up spending too much time/energy trying to drive traffic to an audience that isn't looking for what you're offering. Bottom line: research. That's how I see it, anyway.