Comments means Interaction, and this is what differentiates a blog from an ordinary website.
To increase comments, you need to first and foremost write good content that is engaging.
Be the first to start a comment thread, when you first comment, it increases the likelihood for others to comment
Your content needs to address a problem or provide an antidote to a problem.
You have to present another view that contradicts the normal, for example tell people how you can make a car fly.
Introduce controversy cos it sells any writing.
Use humor when you write, a little comic relief can result in a comment where your reader tells you how your humor helped.
Lastly create suspense and anxiety, this will make any reader want to ask questions by way of comments.