Smiling politely to mask a familiar feeling of desperation, Sarah reminded herself to think like an anthropologist. 'I'm a researcher studying the behavior of boring suburban women. I am not a boring suburban woman myself.
-- Narrator (Part 1, chapter 1 paragraph 1)

Importance: Sarah's characterization is shown immediately, as the reader learns that she is hiding her true self from whomever she is with. She clearly does not feel as though she belongs with the group of mothers with whom she is sitting, nor does it seem she wants to fit in with them. The reader learns immediately that Sarah is one of the main characters, and that her sense of desperation is paramount to the overall narrative.

And when Aaron called out for him just then, right on time, there was something beautiful about that, too, the way a little kid needed you for everything and wasn't afraid to say so.
-- Narrator (Part 1, chapter 2 paragraph 4)

Importance: The way Todd emotionally reacts...