Apply the "memoir contract" with the reader -- shaping true events for effect through compression and reconstructed dialogue -- while staying honest about what actually happened.
A reader trusts that a memoir is true, even though memory is imperfect and a writer must shape real events into a readable scene. Shaping is not inventing: compressing time by skipping the boring parts, reconstructing dialogue as it is remembered rather than as a word-for-word transcript, and choosing which true details to include are all honest, normal craft choices.
The ethical line sits at invention: adding an event that did not happen, or falsely attributing words or actions to a real person, breaks the memoir contract. The test is simple -- could you defend every event in the piece as something that genuinely happened, even if some details are compressed or reconstructed from memory?
Mastery looks like: They distinguish honest shaping (compression, reconstructed dialogue) from invention, and apply the memoir-contract test to their own draft.
Common stumbles: Inventing a dramatic event or exact quote that did not happen in order to improve the story, crossing from shaping into fabrication.