With this in mind what would be important if one is bringing an action against an employer for actions of an employee?

Please keep in mind that liability attaches when an employer knew about the activity and took no action to stop it or they should have known and took action to stop it. With this in mind what would be important if one is bringing an action against an employer for actions of an employee?

Bennett-Alexander, D. & Hartman, L. (2015).  Employment law for business (8th ed.). New York: McGraw-Hill Education Chapter 6