Conducting regular security awareness training sessions is the most effective method to enhance employees' skills and knowledge for identifying and responding to security threats such as social engineering attacks. It equips them with the necessary tools and information to better protect themselves and the company's assets. While mandating the use of complex passwords and implementing multi-factor authentication are useful security measures, they do not directly educate employees about recognizing social engineering threats. Updating the Acceptable Use Policy is important for regulatory compliance, but it does not ensure that employees understand and can act against social engineering attacks.