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This is up to each individual using Canvas. However, as a starting point, Technology Services recommends paying close attention to the notifications highlighted in the following PDFs:
Recommended Canvas starting point notifications recommendations for STUDENTSNotifications to consider for FACULTY.pdf
Canvas Notification Recommendations for Faculty.pdf
As you work with your notifications, note that if you hover your mouse over the name of a Notification (in a web browser, not a mobile app), you'll get a short description of what the notification does. If you really want to get into how notifications, check out this pdf from Instructure (makers of Canvas).