These four tipsheets are about the most important pages in Google Classroom, each from the teacher's side of things. The most common tasks I'm asked about and the most overlooked options are marked with stars.
I am sharing them as Google Drawings so you can copy and modify them as necessary. You can easily download them as PDFs or image files if necessary.
If these are helpful, you might also be interested in my tipsheet explaining the 3 ways to share assignment attachments in Google Classroom.