Lesson 1: Long before the domain name is settled on, start putting together notes to build at least a 100 page site. That's just for openers. That's 100 pages of real content, as opposed to fluff pages like link pages, resource pages, about pages, etc.
"Content is king" is a fundamental theme that you'll see repeated throughout 26 Steps To 15K A Day, because good content is the basis of search engine success. People use search engines to find information, so content is key to attracting organic search engine traffic.
You do not have to create at least 100 pages of content when starting your site. You only need to prepare to create 100 pages of content. That's a big difference!
Essentially, this is a brainstorming step. You start with the general topic of the site (or blog) and flesh it out with lists of categories, subtopics, questions to answer, related topics, etc. Some people like to create mindmaps to capture all the ideas, while others like to create hierarchical lists. It doesn't really matter how you do it, only that you capture the information for later perusal. You'll want to refer to your mindmap/lists frequently as you build up your site. And add to it as the site grows.
But why the focus on content creation, even at such an early stage?