I'm going to pick the example given in the text of the section lesson. "Jem shuddered. “Like somebody was readin’ my mind. Like somebody could tell what I was gonna do. Can’t anybody tell what I’m gonna do lest they know me, can they, Scout?". The sentences are all shorter, simple sentences. Simple sentences are commonly used to portray somebody young or somebody anxious. In this case, it's both. Jem uses this sentence structure because the rhythm and musicality of the words were different than that throughout the novel. This helps them stand out. The short sentences also point out to the reader that Jem is anxious and is having trouble putting his thoughts together.
Its represents a human action, a sun obviously cant peek because we know for a fact it doesn't have eyes, but the author is using personification to describe his point of view of seeing the sun, emotional references.