Leonardo da Vinci's sketching process and techniques provide valuable lessons for designers today. He would sketch prolifically by hand on separate sheets of paper, doing initial sketches alone before reviewing them with others later. His sketches included annotations, arrows and labels for clarity. Da Vinci stored his sketches and would revisit them later, demonstrating the value of saving early ideas. His prolific sketching led to masterpieces and innovations by striving for quantity, deferring judgment, seeking new combinations and using imagination during ideation. When refining ideas, Da Vinci's approach was to use positive judgment first, consider novelty, stay focused, and be able to redirect himself if needed.