Targeting Exactly One Event

Picking the event is half the job. Now you have to fire on only the case you mean. A generic form_submit fires for the newsletter box, the contact form and the demo request alike. If your conversion tag listens for "form_submit" with no further condition, every one of those becomes a demo lead. You need a discriminator: a value that is true for the case you want and false for the rest.

Where discriminators hide

• The event payload: a formId, formName or plan key already on the push.
• The element: from gtm.element you can read the form's id, classes, action URL or a data-* attribute.
• A hidden field: many forms carry a hidden form_type or campaign input you can scrape.
• The page: if the demo form only lives on /demo, Page Path is a perfectly good condition.
• Button or link text: Click Text like "Request a demo" can separate two buttons that share an event.

Then the trigger is two conditions: the event, and the discriminator. For example, fire on Event equals form_submit and Form ID equals demo-request. Now it is genuinely specific.

When nothing distinguishes them

Sometimes two cases share an event and have no clean distinguishing key. Then you derive one. A Custom JavaScript variable can look at the element or URL and return a label; you trigger on that label.

function () {
  var form = {{Click Element}};            // the submitted <form>
  if (!form) return undefined;             // guard: never throw
  var action = (form.getAttribute('action') || '').toLowerCase();
  if (action.indexOf('/demo') > -1) return 'demo';
  if (action.indexOf('/contact') > -1) return 'contact';
  return 'other';
}

Clean up the messy values you find

Discriminators in the wild are rarely tidy: demo-request, Demo Form, frm_3 might all mean the same form. Don't scatter those raw strings through your triggers. Map them once with a Lookup Table (exact matches) or a RegEx Table (patterns) into one canonical name, and trigger on the clean output.