When an author describes a character, he is revealing much about this individual. Author descriptions give readers the opportunity to create pictures in their heads of the characters present in the text. The ways in which authors tailor these descriptions can play a large part in determining how readers view the character. If an author describes a character in a complimentary fashion, readers will likely get an immediately positive impression of the character. Conversely, if the description is negative, readers will likely immediately dislike the character.
The ways in which a character interacts with other characters tell readers much about who the character is and how he is perceived by others. If a character's interactions with others are largely peaceful, readers will likely view the character as an amenable individual. On the contrary, if his interactions are characterized by strife, the readers will view him as a character who is difficult to get along with.
Both the things a character says and the ways in which she says them tell readers about the character. Particularly when a story is written in third person fashion and, as a result, readers are not in the character's head, what a character says to others may be the only way for readers to get insight into a character's thoughts. The types of words the character selects as well as any dialect the character tell the reader about the character's intellect and background.
In some stories, the readers are not left wondering what characters are thinking, but instead are given clear insight into the character's thoughts by seeing into the character's mind. When an author writes in first person, he allows readers to step into the character's mind, revealing much about the way in which the character thinks and feels.
The physical actions of a character give readers insight into a character's wants and needs as well as his values and morals. If a character follows a proper and polite path, the reader will see the character as morally correct. If the character instead does not shy away from inappropriate actions, the reader will see him as an amoral character and likely an antagonist.