I would like to offer a slightly different definition of "narrative conventions." The items named by the previous poster -- "points of view, character development, descriptive language, conflict, climax, plot, theme, etc" -- can certainly fit under the term, but the term means a lot more than that. At least to me it does.
Narrative conventions are the extremely common and easily overlooked patterns that we've grown to expect in stories that we encounter. They certainly do include character development, for example, but they can also include slightly more abstract ideas, such as exemplification, or specific patterns or techinques of storytelling, such as realism or the bildungsroman (the novel of development).
On exemplification: As an adult reader, I rarely enjoy stories that end with a strongly phrased moral lessons, but I do tend to enjoy stories that present moral or ethical issues through well developed and extended examples. To me, To Kill a Mockingbird can be read as presenting issues in a fairly complex way. For example, I can read the novel and find myself agreeing or disagreeing with the covering up of Bob Ewell's murder at the novel's end. The story may prompt me to agree with the cover-up, but I'm not required to.
On realism and the bildungsroman: Lee's novel is certainly written in the tradition of realism, seeking to recreate within the covers of the book an entire community, with its complex hierarchies and conflicts, and using a narrator who is removed (by several decades) from the community that she is describing. At the same time, To Kill a Mockingbird is also a tale of development of one or more children who are central to the story.
I haven't had much luck finding a good link on narrative conventions in novels, but I did find something that addresses narrative conventions in popular TV sitcoms.
Narrative conventions include points of view, character development, descriptive language, conflict, climax, plot, theme, etc.
In this novel, racism is represented in several of the narrative conventions. I will get you started on some, and you can take it from there.
Plot - A main plot in this story is the accusation of rape and subsequent trial of Tom Robinson. Tom is black and has been accused of rape by a white trash white woman. He is not guilty. Atticus Finch defends Tom and even though Tom is convicted due to the racism in the town, Atticus puts up a brilliant defense. The blacks in the community stand when Atticus leaves the courtroom to show their gratitude. During the trial, Scout and Jem are constantly defending their dad's decision to "defend niggers."
Characters - There is the character of Tom Robinson. He is a rather stereotyped character but his character illustrates the racisim prevalent in the South at the time. He is a good man, but he is poor, black and uneducated, and a scapegoat to be blamed for a rape that never occurred. Mayella Ewell accused him of raping her to protect herself from her crazy father because, in actuality, it was SHE who tried to seduce Tom.
Also, the character of Calpurnia illustrates racism. Calpurnia is the Finch's maid. She is wise and intelligent, but another black stereotype. She reverts to "her own language" when she is under stress or among her own people, but when she is working among whites, her language is that of an educated person. It illustrates how blacks were forced to act in different ways, depending on where they were.
Setting - The story is set in the South, where racism was more prevalent. Also, the blacks live on the other side of town. Calpurnia takes Scout and Jem to that part of town from time to time, and they stand out because they are white. They are uncomfortable. Also, Atticus visits Tom's wife on that part of town and is spit on for being a "nigger lover." Also, during the trial, Scout, Jem and Dill sit in the balcony, with the "coloreds" - not in the regular courtroom. Atticus has told them not to come to the trial, but they come anyway and are embraced and protected by the blacks.
Get the idea? Now you can do the rest. If you are writing an essay, perhaps you will want to limit your subject to one or just a few of these elements, because there are so many in the novel. Racism is one of the themes, so naturally it is going to permeate all of the narrative conventions.