GA4 can collect hundreds of events and still fail to answer whether marketing created qualified demand. A measurement plan prevents that failure by connecting each event to a question, owner, definition and decision.
1. Start with decisions
Write the recurring decisions first: which channel to fund, which landing page to fix, which audience to exclude, which content assists pipeline. Then define the minimum data required for each answer.
2. Design an event taxonomy
Use clear lowercase names, stable parameters and one definition per event. Separate business outcomes from interaction diagnostics. Mark only actions that matter to the business as key events.
3. Specify consent and data quality
For every event document trigger, parameters, consent state, retention need, owner and test case. Never send personal data in URLs or event parameters. Expect modeled data and attribution updates; communicate this in reporting instead of presenting every number as final.
4. Run a release checklist
Test in debug mode, verify consent states, submit real forms in staging, compare the browser request with GA4 and CRM, and monitor the first 48 hours after release. Monthly reconciliation catches silent failures before they distort budget decisions.