Include a table of contents or other guides
Tables of contents accelerate finding information and help readers know what they will find without frustration. This increases the likelihood they will stay to read your content if they find it interesting or useful, instead of leaving because it was unclear. If there are multiple levels to your organizational hierarchy for the document, consider not only how the information fits within the document, but also on the page.
For example: this page not only has the left sidebar, but also a page-based breakdown in the top right corner showing what is on this page.
Dynamics in Document Design: Creating Text for Readers. Karen A Schriver, 1997.
Structuring Documents According to Their Table of Contents. Hervé Déjean and Jean-Luc Meunier, Proceedings of the 2005 ACM Symposium on Document Engineering, 2005.