There are situations when we are handled an old dashboard or not build correctly and the goal is to re-design and make it useful for the analysis.
The main page is showing us the Problem and What we need to achieve.
(hyperlink)
The guide is self-explanatory and show main aspect of the design tips applied.
Here it is a good representation of how you can create a "Corporate Palette" and spread over the company and make sure everyone's using same approaches as the goal is to have the dashboards with the same Feel and Look.
Some instructions on the "Whitespaces" and how to use additional objects and Padding.
All details are covered in the dashboard itself and the purpose is to spread good design tips across Tableau Enthusiasts.
Happy Vizzing.