Engage readers with well-researched and creative blog posts. At the end of it ask questions or feedback from them.
Add your personality - If you are writing on a particular topic, there are a number of people who will be writing on the same topic. So you need to add that specialty to your blog to make it look different and to allow your readers to take away something that the others are not offering.
Bloggers are writers. Even if you're into photography, video making or sketching and drawing.. and are blogging about those skills, you need to write well.