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.
Include data in blog posts. It makes the post more interesting and informative to read. It makes people stay longer on your pages and even share your content.
Picture talk: Use of images attracts more eyeballs. It is humanitarian. Even if it is a data centric post or a theoretical one, have an image that speaks significantly for your post.