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.
Remember that content is the key to a successful blog. Quality scores over quantity in getting audience to your blog.
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.