Pinterest Campaign Essentials
Pinterest publishes a document called Campaign Essentials, and it is a good source for best practices, tips, and tricks for running Pinterest campaigns. You can find it here:
Get your website ready for Pinterest
How to start using Pinterest for your business
The very basics and first steps about How to start using Pinterest for your business.
Pinterest creative best practices
Pinterest creative best practices article has tips about the essentials for Pinterest creatives as well as how to adjust your creative based on your objective.
Pinterest has some creative inspiration also on these boards:
Promoted Pins best practices
The Pinterest Webinars YouTube playlist has a good set of webinars and tips about optimization, as well as dos and don'ts.