You want elements such as headers, sub-headers, lists, tables, sidebars, and footnotes that complement the work without your readers being distracted.
This is why I'd highly recommend using a professional layout program. Layout and typesetting are other critical components. Once thinking about the writing became thinking about the design, the writing became much easier - it was just another aspect of the design. You want something aesthetically beautiful, whatever beautiful means for the work that you're creating. You want the layout to complement the text and the text to work with the design. This realization was that writing and design are not two separate things. First though, I wanted to talk about a realization that helped me get past a few of my writing hurdles. We'll be getting to the marketing aspect, it's the hardest part for me as well.
In a poll at the end, skywriter asked about the hardest part of self-publishing and two themes emerged: writing the book and marketing the book. It's a great read and the follow-up discussion was also extremely valuable. Last week, skywriter published an excellent piece recommending indy publishers consider both CreateSpace and IngramSpark.