Here are the main things you must do as a leader
Be aware of the things going on around you and be conscious of your role as a setter of standards
Be willing and able to speak out early. Have the words to be able to gently yet firmly correct inappropriate behaviour before it escalates.
Get a coach if you need support or guidance on how to do this. I’m happy to speak with you if you need support.
Be clear on the standards that you seek. Discuss those standards and the behaviours that are associated with them, as well as the behaviours that would contradict or undermine them. Have those discussions with your peers and your staff.
Be willing to have robust conversations to help staff understand those standards.
Be willing to not hire or promote someone if they do not meet those standards. Be willing to take corrective, including disciplinary, action.