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.
Keyword search: Take up a keyword search for the blog posts you are writing. Choose the ones that searched often and have less competition.
Originality - Focus more on the originality of content and on a consistent basis. It is a habit you will need to cultivate.