A wise man can read people's faces and expressions - with the result being that of being warned against those who are planning perverse and evil things. In the Jewish world the winking of an eye was considered an evil thing. This kind of facial movement was consistently condemned as we read in Proverbs 6:13 as well as in Proverbs 10:10 where we learn that the one who winks an eye is doing so to cause trouble. Even in Psalm 35:19 this is seen as an ungodly thing, where we read of those who "wink maliciously" as they plot evil. Such a wink is considered part of the shiftiness of those who are plotting and scheming against others. Therefore the godly man who is wise will note such things and weigh their words on the basis of their signals.
Note that the "winker" is one who is devising "perverse things." The word for "perverse" is "tahpukah" which means to deviate and distort God's ways. It is interesting that when men are acting perverse, they are first seeking to pervert God's ways. They are deceptive in their intent and are corrupt as they speak. There is a perversity in their hearts that disregards God's Word and His ways as they plot their evil and their conquest of others.
We are also warned about those who "compress their lips." We are told that they do this to bring evil to pass. The picture that we should get is someone who is putting their lips together and pressing them tightly. This expression, as we are told by several Hebrew commentators, is a sight of anger, rage, bitterness, and disgust. The one who does this has no good planned. There will be an "evil" that will come to pass from such a man.
Wise men notice a man's visage and face. The face of those who are godly and loving will be one that is glowing and hides nothing from others. They are usually people filled with joy and with the peace that arises from having a relationship with God where they have been justified and declared righteous in His sight by the gift of His grace. The wicked man cannot hide the evil that resides in his heart. It is etched into his face - and in the tightness of one whose true motives cannot be brought to the surface for fear that they will be exposed for what they are - perverse and filled with misery and evil. Read a face, dear saints of God, and you will often understand a heart.