The Evolution of a Blog by a Cromagnon Man Eager to Develop

I must admit that Blogs tend to confuse me, but I gather they're rather wide-open with regard to chosen content. My main objective is to promote my novel, Silent Battlefields, best obtained on Amazon (my web site address: www.hughrosen.com). However, I can write about a wide variety of subject encompassing such topics as creative writing, psychology, psychotherapy, philosophy, morality and so forth. any advice from others as to how to proceed. It would be most welcome and appreciated. Hugh