Spare time to read - Blogging is not just about writing but also about research and reading. Read as much as you can to learn new things and ideas that you can experiment with on your own blog.
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.
Use technology - Social plugins and SEO tools are a great thing to market your blog or a blog post. If you do not know about it, then learn it. It helps you reach out your audience in a better way and also improves the ranking of your blog.