Image speak - A lot of bloggers tend to ignore this, but the images on your blog speak a lot for what you write. Use good quality images and make sure they express your written stuff in utmost simplicity yet precision.
Respond with personalised comments rather than a generic Thank You. Fostering a conversation helps build the credibility of your blog!
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.