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.