In the area of contrasts, there is a selective discrimination in the southern town of Maycomb that should not be overlooked, for it is not untypical of such a setting (both time and place). For example, Calpurnia, the Finch's housekeeper, fills a motherly role for Scout and Jem. As a wise and loving person, she provides the children with many experiences that allow the children to be more objective in their judgments of others.
This loving relationship between African-American household employees and the children of the owner's family was prevalent in many situations in the South. Yet, while the children always remembered the housekeeper fondly, and talked with her any time they met her as adults, there was often a bias against other people.
Likewise, there is a selective tolerance for people of oddity who did things outside the restrictions of society. Such an example is Mr. Dolphus Raymond, whose wife and children are black, is tolerated since he "drinks." Raymond knows that if he puts his cola bottle in a paper bag, people will think he drinks and, therefore, excuse his behavior.
By the way, besides the excellent tips you have already received, you may want to go to the cite on "how to" for steps on how to write an analytical essay.
Using the theme of discrimination, you might want to consider how the family of Boo Radly treated him. In bygone days, persons who were different or "mentally ill" were sometimes kept away from everyone else. You might consider all the ways that Boo Radley showed kindness toward the children in the story as compared with all of the "wild stories" about what Boo Radley did after dark. How was Boo Radley discriminated against?
Using the theme of discrimination, you might also compare the different types of discrimination in the story. There is racial discrimination as well as discrimination against a person who is "ill" and shut away from society. How are these two types of discrimination alike? How are these two types of discrimination different?
Finally, there is the reaction of Tom Robinson and Boo Radley to the various types of discrimination. What happened to Tom after his experience of racial discrimination? What happened to Boo Radley after he was discriminated against for being "mentally ill"? How are each of these men "separated" from society as a result of discrimination?
And finally, there is the theme of reverse discrimination in relation to Atticus as he defends Tom Robinson. How is reverse discrimination different from overt or direct discrimination as related to Atticus Finch and Tom Robinson?
if you are being asked to contrast something, you are usually being asked to show how two or more things are different. As far as "To Kill a Mockingbird" is concerned, there are some people who do not seem to discriminate against the African Americans in Maycomb and another group which does. You could show the difference in each group's behavior or use two characters as examples of people who discriminate and those who do not. For example, you could compare Aunt Alexandra's behavior and dialogue with that of Atticus. Even though these two characters are brother and sister, they show different attitudes towards the Black population of Maycomb. You would begin with a thesis statement about how each of these characters differs in their attitudes. The body of your essay would be composed of examples of their behavior and dialogue ( quotations) that would show how each character behaved and what each said. One paragraph might show how Aunt Alexandra behaved toward Calpurnia, how she felt about her brother defending Tom and what she said to her son about Atticus. Another paragraph would contain examples of how Atticus showed the opposite attitude. Your conclusion would then summarize the differences between the two characters in their actions towards African Americans. Hope this helps.
Contrasting means to show the difference between something. Since this story is mostly about discrimination, you could choose to contrast the family characters such as the Finches versus The Cunninghams
Or you can contrast the protagonist who happens to be Scout to the Antagonist who happens to be Mr. Ewell and use their views on discrimination as examples.