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.
Always acknowledge a comment on your blog and respond to the commentator, preferably at his own blog. Its great to reciprocate the gesture.
Choose a template that suits your blog content. It not only adds to the blog's beauty but will also accentuate the content well. Bad design is always a put-off to readers.