Tags: Use of relevant tags is important from the SEO perspective. It helps the search engine track your post based on the tags you use.
Variety is the spice of life so spice up your blog now and then.
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.