First, it is important to identify items in the novel that have symbolic value. For example, the slingshot-- used by Hassan and Sohrab-- factors heavily in two important scenes in the novel. They are symbols of strength, and remind me of the biblical character of David, who was young and weak but was able to use it to topple a mighty opponent.
The kite is also an important symbol, which implies a freedom that many characters hope for but is very difficult to find. Amir wants to impress his father, while Hassan pays a heavy price for the kite's return. It is not until the end of the novel, when Amir shows Sohrab how to fly a kite and fight with it that both Amir and Hassan's "freedom" is realized.
Hopefully this is a helpful starting point for you.