The skill of observation is simply to see with your eyes. The other side of communication often unconsciously expresses his inner activities in a nonverbal way. In addition to verbal communication, observers can also collect useful information by observing each other's expressions and actions with their eyes. Sometimes the information obtained by observation is more valuable than the information obtained by ear. That's what "hearing is false, seeing is true" means.
The observation skills are mainly careful, comprehensive and keen. When observing, you should be very careful, have a keen eye, be good at capturing subtle changes, and be able to discover deep inner activities and covered facts through superficial phenomena, so as to obtain real information. However, careful observation should be based on sincerity and calmness, instead of ignoring each other's words and turning your eyes to other places, let alone turning careful observation into voyeurism. That is not a normal observation skill, and the other party will inevitably resent it, leading to communication failure.