This document discusses several techniques for improving the understandability of textbooks: 1) Coherent cognitive structures help learners build mental models of the text and learn by making connections within and between concepts. 2) Adjunct questions guide learners' attention to important parts of the text as they read. 3) Signaling with techniques like headings and summaries helps learners organize the text and identify key information and shifts in topics. 4) Advance organizers provide context before learning to help learners integrate new concepts with prior knowledge.