Call-to-Action Buttons and Techniques
A great article from Boagworld:
https://boagworld.com/design/10-techniques-for-an-effective-call-to-action/
Smashing Magazine also has a great round-up from 2009:
https://www.smashingmagazine.com/2009/10/13/call-to-action-buttons-examples-and-best-practices/