Over on Creating Passionate Users, there is a post about starting presentations, articles, and books, where Kathy Sierra goes over what to do and not to do so that you have a better start. This translates well for blogging, as holding the attention of someone reading your posts can be very difficult.
Challenge a belief. Even if they instantly disagree, they’ll stick with it long enough to find out where you got that crazy idea. Start with your most dramatic and/or unpopular assertion.
Start with a story about real people, or about a fictional character they can identify with.
Do something surprising… VERY surprising
They’ll want to stick around to see what strange thing you do next.
The rest of the points listed are just as profound. A great article, and some sound advice.