How to install Google Analytics on Blogger

There seems to often be confusion as to how to install Google Analytics to Blogger (blogspot) blogs

Last I looked there were instructions for installing the Traditional version of the tracking code into a widget, or for installing the Traditional version of the GA tracking code before the closing </body> tag, however none seemed to really address in detail how to install the current Asynchronous version of code in a simple to understand way for new users.

Whilst the Async version of Google Analytics tracking code can be installed before the closing </body> tag, often other script within the blog layout can interfere with it working correctly. The same applies to placing the Async tracking code into blogger widgets.

So, lets get started ...