For DIY maintenance, you can replace air filters regularly, clean the AC unit's exterior, ensure vents are unblocked, and maintain clear space around the outdoor unit. These tasks help improve efficiency and air quality. Professional maintenance should include checking refrigerant levels, inspecting electrical components, cleaning coils, and ensuring the system operates safely and efficiently. Professionals have the tools and expertise to diagnose and repair complex issues, ensuring your system's longevity and preventing costly repairs or replacements down the line.