If you're into design, you may know Invision, the app that grew quickly as the by-default prototyping tools for most designers.
The firm creates a lot of content to help newcomers master design skills. A few month ago, they created designbetter.co, a ressource platform dedicated to good conception practices.
The idea here is to help you and your company create a common design language, allowing your team to work better and faster next time.
The handbook is worth exploring, and, as always with invision, beautifull !