Most of the characters in The Lion, the Witch, and the Wardrobe are characterized by their actions. Mr. Tumnus is good because he acts to protect Lucy, rather than turn her over to the White Witch. Peter is brave, not because he feels brave, but because he kills Fenris. Edmund doesn't tell his brothers and sisters that he has turned against them, he simply goes and tells all their plans to the White Witch. What people do in this world shows us who they are underneath.
In Narnia, things are usually as they appear to be. The Witch's extraordinary pallor is a clue to her unnaturalness. Aslan's golden mane demonstrates his regality – and even after it is shaved off, he grows it back, because it's an expression of who he truly is. When Edmund is getting ready to betray his brothers and sisters to the White Witch, Mr. Beaver can see it in his eyes. You get the idea.
The narrator of The Lion, the Witch, and the Wardrobe rarely hesitates to tell us what someone is like directly. For example, we are told that Peter is brave, that Susan is motherly, that Lucy is courageous, and that Edmund started to become unpleasant because he went to a bad school.