Common mistakes in the installation of lightning protection system include improper grounding, which can lead to ineffective dissipation of electrical energy. Another mistake is incorrect placement of air terminals (lightning rods), which may not provide adequate coverage or protection. Using undersized conductors or poor-quality materials can also compromise the system's performance. Additionally, failing to follow local codes and standards or neglecting routine maintenance can reduce the system's effectiveness. Ensuring professional installation and adhering to safety guidelines is essential for reliable lightning protection.