To successfully implement GTM you need to cover 9 planning steps.
Macro level – migration planning
- Getting IT buy-in & determining client development resources
- Review existing GA installation
- Tactical planning
- Technical planning
- Conversion trigger planning
- Naming conventions plan
- Quality assurance process
- Reducing human errors (IT dept on-boarding & training process)
- Security planning on Google Account
These 9 steps are covered in the next sections. Additionally, the outcome of each phase such as technical planning, could have micro phases. For example using “parallel” deployment micro phases:
Micro level – deployment planning using a parallel tag
- Create empty GTM container and add the code to global header of ALL pages.
- Deploy parallel deployment of Universal via GTM, with GA classic running via hardcode.
- Find & replace GA classic code with event called onload_ga_pageview.
- Add ecommerce dataLayer to checkout thankyou page
- Replace inline code gaq.push with equivalent dataLayer.push code and add GTM event tags within GTM settings, so there is a seamless migration.
- Add better dataLayer for product pages and user-interactions.
Tip: A Google quick start implementation plan is shown here.