A Measurement Plan Before You Tag: The Template

The teams with clean analytics almost never started by opening GTM. They started with a measurement plan, a short document that says what the business needs to know, which events answer that, and what data each event carries. Skip it and you get a container full of half-tracked events nobody trusts. Here's the template.

Why plan before you tag

Step 1: business goals → events

Start from what the business is trying to achieve, not from what's easy to track. Work down from goal to question to the event that answers it.

1. Goal: e.g. "grow online revenue."
2. Question: "where do people drop out of checkout?"
3. Events: begin_checkout, add_shipping_info, purchase.

Step 2: the measurement plan document

It doesn't need to be fancy, a single table everyone can read. For each event, capture:

• Event name: the exact string (e.g. generate_lead).
• Trigger: when it fires (form success, button click, page).
• Parameters: the data it carries (value, currency, form_id).
• Priority / owner: is it a conversion, and who needs it.

Step 3: design the dataLayer schema

Decide the exact shape your site will push, before anyone writes code. Consistent keys and types make every downstream variable trivial.

dataLayer.push({
  event: "purchase",
  transaction_id: "T-1042",      // string, always present
  value: 49.0,                   // number, no currency symbol
  currency: "USD",               // ISO code
  items: [
    { item_id: "SKU_1", item_name: "Cap", price: 49.0, quantity: 1 }
  ]
});

Step 4: write the tagging spec for developers

Translate the plan into instructions a developer can implement without guessing: which event to push, on what user action, with exactly which keys and types. A good spec is the difference between "tracking works" and three rounds of back-and-forth.

What a spec row contains

• The user action ("on successful checkout").
• The exact dataLayer.push object, with example values.
• Notes on timing (push before navigation) and edge cases.