With very few exceptions, employees should report managerial misconduct in writing. The complaint should be sent to Human Resources (depending on the relationship of your manager’s boss you may consider copying that person as well). The complaint should be sent by email so there is proof of when and to whom it was sent. The email should have a professional tone and set forth the allegations and the factual basis to support them. Otherwise, without a paper trail employees leave themselves exposed to claims that they never reported the matter or that they did not provide all of the information.