You should a half dozen or so sections. None of these chunks or nodes should be longer than the equivalent of three computer screens. Now you need to create the headings for these sections. If your document already has headings, make there are enough headings and that they are descriptive enough. It's important to have plenty of headings and to have rather verbose, fully descriptive headings in hypertext.
Headings are one important way to enable readers to know where they are, where they are headed.
Don't stop with just one main heading at the top of each section though. If a section breaks cleanly into subtopics, make headings for those as well. Take one of your markers and write these headings right into the sections where they belong. Create the main menu. Take a blank sheet of paper, write the title of the document centered at the top and then each of the main headings as an item in a bulleted list below the title.