List critical junctions where hesitation, distraction, or uncertainty appears, such as login prompts, shipping forms, or calendar handoffs. Capture intent, expectation, and context at each step. If measurement feels hard, your definition of the step is probably imprecise or overlapping.
Track cognitive load with proxy signals like backtracks, corrections, scroll depth, dwell time, or repeated taps. Interview a handful of users to surface wording that confuses. Friction rarely shouts; it whispers through abandoned fields, misclicks, and apologetic error messages.