S.E. Hinton uses figurative language such as similes, metaphors, personification, repetition, and alliteration.
California is like a beautiful wild kid on heroin, high as a kite and thinking she's on top of the world, not knowing she's dying, not believing it even if you show her the marks.
In this quote, we see a simile comparing California to a kid on drugs. We also see personification, as the state of California is given human qualities and emotions in the comparison.
Hinton also uses simile when describing Steve:
He looked like a sincere rabbit about to take on a pack of wolves.
Similes and metaphors are both comparisons, but similes use "like" or "as." The comparison in the quote below is a metaphor:
Your mother is not crazy. Neither, contrary to popular belief, is your brother. He is merely miscast in a play. He would have made the perfect knight in a different century, or a very good pagan prince in a time of heroes. He was born in the wrong era, on the wrong side of the river, with the ability to do anything and finding nothing he wants to do.
This metaphor compares Motorcycle Boy to an actor being cast in a show. We also see alliteration in "merely miscast" and "pagan prince" with the repeating first letters. Repeating the word "wrong" emphasizes how out of place he is.
Repetition is also in the following quote:
I love fights. I love how I feel before a fight, kind of high, like I can do anything.
Hinton also uses the literary device of flashback throughout the whole story.