How does the author reveal the character?

I'm assuming your talking about Holden?

Holden Caulfield

The narrator and protagonist of The Catcher in the Rye, Holden is the son of a wealthy New York family who moves from boarding school to boarding school after being repeatedly expelled. Although he displays a number of typical teenage characteristics, his adolescent foibles become increasingly disturbing throughout the novel, revealing a self-destructive side. Holden, it seems, has been particularly devastated by the death of his brother Allie, who he considered the perfect child. This has thrown him into an existential crisis of sorts; he is unable to find joy in life or to cope with his loss. Ultimately on the brink, he capitulates to convention and comes back home, though there is little sense that he has found even the basic ingredients for happiness.