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.
For E-commerce bloggers, it is essential to define your audience and take worthy steps to reach out to them. This will be the sole determinant of your marketing plan.
Keyword search: Take up a keyword search for the blog posts you are writing. Choose the ones that searched often and have less competition.