The Clay Global guide to diary study UX provides a comprehensive methodology for balancing depth and participant engagement. Start by defining "signal moments" - critical behaviors like failed transactions or security concerns - then create trigger-based prompts (e.g., "Take a photo when you feel anxious during payment"). For mobile banking, combine scheduled daily check-ins ("Rate today's banking stress 1-5") with event-triggered entries ("Record voice note after transferring money"). Clay's phased approach segments your study into orientation (training participants on quick video logging), main tracking (7-10 days with decreasing prompt frequency), and retrospective interviews to contextualize findings. Their sample banking study reduced dropout rates to 12% using micro-tasks under 90 seconds, while timestamp analytics revealed hidden friction points during commute hours.