You may have already read a dozen guides on basic blogging, WordPress installation, theme choice and installation, maybe even customization. You might have even read some guides on SEO for WordPress or how to write great content.
The trouble is that great content is not always content that will help you achieve your objectives. Great content is not always what sells.
You can write the most helpful, interesting content in the world and make no money from it simply because you haven’t written the content in a way that makes sales.