I assume your instructor is interested in you recognizing some differences between western culture and Afghani people? Afghani's pride themselves on familiar relationships, hospitality, and peace (among other qualities). What makes the novel so interesting is that so many of the characters occassionally violate these norms, while at other times they are strictly adhered to qualities that separate the human from the inhumane.
To answer quickly, Kite contests come first to mind. Everybody participates (watching, flying, or chasing kites.) There are strict "rules" that are understood as a cultural practice--ones Assef clearly violates. The contest is more than just about flying kites too; it brings families together, gives reason to celebrate and promotes peace between neighbors.
Family (blood) is also valued in the culture. And these bonds are unbreakable. Saraya breaks cultural norms established concerning male and famale relations but her father still insists customs are followed in Amir courting his daughter. Hassan's mother "Sasa" also violates these norms but is later openly welcomed to his home. Baba most often falls short in this area with his sons but more often will stake his own fortune, reputation or even life upon the line to protect others--simply because they are Afghani.
Note too that the Afghani's settled near one another in an area near Fresno, California where they marketed garage sale items in a Afghani flea market each weekend. This, as Amir indicates, was less about selling items than about gossip and fraternizing.
At the end of the day, the book celebrates a resiliant people and a culturally rich heritage--some that are strictly or only Afghani.