Enable preview mode
To enable preview mode, click on the arrow next to the publish button and select Preview.
Use preview mode
Once the preview mode is enabled, navigate to the site where the container is implemented in the same browser tab and you will see a debug console window at the bottom of your browser showing detailed information about your tags , including their firing status and what data is being processed.
Google: Preview and debug containers
Google Tag Manager for Single Page Applications
Codeproject: Google Tag Manager
Campaign Tagging using Sitecore