When I kept a running journal to log my mileage, I ran more often and ran more miles. Keeping an active blog about what's going on in my life as a musician has the same effect. If I set a goal for myself and then write about it, I'm more likely to follow through. Creating substance for a blog requires creating substance in your life. For me, the topic is music, but you can blog about anything. What you write about helps readers relate to you, how you write it can create more attention, but why you write about it is what keeps things interesting.