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.
A new blog should not add to the existing noise in the blogosphere. Do something outstanding to get noticed.
After completing your post, read it with a fresh eye from the perspective of a reader to check if you enjoy it or if it needs changes.