As writer's we're told to create a blog to garner interest in who we are and what we do. The point is to generate PR and market ourselves and our works. Yes, we are selling who we are and what we do on a weekly or daily basis. The question is how do we do that with the least amount of effort?
The answer- know yourself and know your audience.
A good example is my friend Carrie Lofty. She loves to write historicals set in unusual places. She created the blog Unusual Historicals. Where she gathered other authors who write so called "unusual" setting and reached fans of historical romances with unusual settings. (By unusual, we mean places outside the publisher's marketing research of Scotland and England. Places like Spain, Germany, Africa and the Middle East.) Simply by knowing who she is and what she writes, she has succeeded in reaching and building an audience with her blog.
Sherilyn Kenyon created a whole world based on vampires and some say she is responsible for the huge wave of vampire stories now. When she first started out there was no interest in the subject- but she created a dark website and built a community of loyal fans who demanded her stories.
When thinking about marketing and where to begin or how to revamp, you should think long and hard about what it is you want to do and who it is you want to read your work.
It is simply, really, know yourself, what it is you do, where it is you want to go and know your audience. Everything else stems from there.