Audience quest: Pay attention to what your audience is asking and give them what they are looking for in your blog. Whether it is content or questions, make it interesting.
Series of articles - Create a series of articles on your blog if the subject you choose to talk about is an extensive one.
Grammar - Depending on the language you use, blogging just makes it imperative that you are reasonably good with your grammar skills and proficiency if not a master. Remember your audience is a mix of both; the ones who are experts and the ones who are not.