Andrew Sullivan is a pretty well known political blogger that has contributed to Time, The Atlantic, and The Daily Beast over the years. In the following video, Sullivan provides some tips on blogging, including one that I think is more than a little debatable.
According to Sullivan, you must be posting at least twice a day otherwise "you're just a website," as if that's some kind of bad thing. Unless you're making a living as a blogger or there are multiple contributors to a blog, I'm not sure that most people can post that often. SFDB manages to that through scheduled posts but even at that, two of those posts are Sifts that are really a review of other activity in the South Florida blogosphere. Personally, I think a blog needs to post daily in order to retain a regular readership, although there are plenty of South Florida blogs that don't that still are very readable and are certainly "blogs" by every definition of the word.
The other two main points of Sullivan's advice, i.e. being yourself and creating a dialogue versus delivering a monologue, I would agree are certainly relevant to good blogging. I have to say that the dialogue thing can be very difficult given the potential disposition and biases of some of your readers, especially when it comes to politics, but the alternative is to create an echo chamber where comments consist almost exclusively of "attaboy!,"excellent point!," and other self-aggrandizing pronouncements. See Babalu Blog for further explanation.
So take the following rather preachy advice as a guide rather than the Bible.