Define the six core events
The six moments your funnel turns on, named once and never renamed. Subscription: signup_started, signup_completed, activated, trial_started, subscribed, cancelled. One-off purchase (a kit, a template, a course): product_viewed, checkout_started, purchased, downloaded_or_installed, first_use, refunded. Usage-billed or free-with-upsell: pick the six that mark the same turns. The names matter less than never changing them.
Step 1.1.1.2
Time: 45m
Done when
List the six event names as they are written in the code that emits them. Six distinct names, none of them a rename of an earlier one. (Proof: a list of the items.)