Practice what you preach
Leaders should practice work ethics themselves before urging their employees to follow suit. Do it first and your workers will definitely follow.
Acknowledge and reward those who practice them
Reward employees who practice good work ethics. It need not be much, it could be an email that is copied to the rest of the company or a small token of appreciation presented to the employees. This will serve as a reminder to the rest of the organisation of the importance you place on ethics and etiquette.
Reprimand those who go against work ethics
If a worker is caught going against work ethics, that person should be reprimanded, no matter how small the fault is. This shows that you are a leader with principle and sends out a strong warning to all the other employees.