1. First, make sure you turn the power off. There may be a switch on the side, or there may be an outlet to unplug. Just make sure it's off.
2. Vacuum the slats (also called fins). This removes any debris that may be blocking air flow from the unit.
3. Clean inside the unit by unscrewing the grill fan and removing from the unit. Use a vacuum hose to gently remove any debris from the interior side of the slats. Be careful not to use too much pressure as this could damage the slats.
4. Finally, put it all back together! Replace the grill fan and screw it back in, flip the power back on (or plug it back in), and reap the benefits of a properly working and efficient AC!