Good breaking dawn, everyone!
Reason Number Symbolism - If your symbol is an object, it'd better have some use in the plot or to the character. Literature nowadays have no depth, and no one is holding a gun to your head and forcing you to use symbols in your stories. In fact, symbols come naturally; the more you force them into a story, the more readers will realize this and turn a blind eye to it. While I realize this could just be my own personal preference, I was reading through a friend's story today.
I asked something like, "What is this [ring] for? What function does this have in the story?" because I was curious. It was random and had no relevance, in my opinon. He replies, "It symbolizes a promise made between two good friends."
Fair enough. The meaning is right. But the story wasn't about promises (*at least not yet), nor was it about two good friends. In fact, the ring was given to the character as a hand-me-down from his mother. The ring wasn't even used as a catalyst to a reminisce about his mother, nor did my friend ever intend on writing the character giving it to the other person.
*A problem with critiquing chapter by chapter, but this was the next-to-last chapter.
Symbolisms are composed of two things: a literal meaning and a deeper/metaphorical meaning.
Look at Ray Bradbury's Fahrenheit 451. Take a look at the river, which symbolizes transition. It helped Montag get away because it's flowing water. Or look at the white handkerchief in Shakespeare's Othello if you like Shakespearian plays (which I do). The handkerchief was used by Iago to deceive Othello and is symbolically the loss of Othello's composure (a meaning my student teacher rejected). But sometimes, a river is just a river or a handky is just a handky.
So... end of point.