One of my personal favorite quotes comes when Scout comes home after her first day of school, dejected by her teacher's instruction that Atticus not teach her to read anymore. Atticus promises to continue with their evening readings as long as Scout continues going to school. To solidify this promise, Scout prepares to spit into her hand for a handshake, and Atticus tells her, "We'll consider it sealed without the usual formality" (28), demonstrating his keen sense of humor.
Another moment where Atticus displays a knowledge of his children's antics comes after Miss Maudie's house catches fire. Atticus tells the children that perhaps they can thank Arthur Radley for wrapping her in a blanket on that cold night; the children were so caught up with the fire that they had not noticed Boo there. Jem begins to excitedly act out Boo's emergence from the house, and Atticus dryly tells him, "Do not let this inspire you to further glory, Jeremy" (66).
Atticus tries to explain to Jem and Scout the true meaning of courage after Mrs. Dubose dies. He tells them that though she was quite contrary, she had battled an addiction in her final days and had left the world free of the drug's control over her, which Atticus admires. He explains,
I wanted you to see something about her-I wanted you to see what real courage is, instead of getting the idea that courage is a man with a gun in his hand. It’s when you know you’re licked before you begin but you begin anyway and you see it through no matter what. You rarely win, but sometimes you do (103).
Following the night when the angry mob comes to Tom Robinson's jail cell, Atticus explains to his children that each of those men is still an individual person, and there are actually decent individuals in angry mobs. Jem is confused, pointing out that they wanted to harm Atticus. His father explains,
Son, you’ll understand folks a little better when you’re older. A mob’s always made up of people, no matter what. Mr. Cunningham was part of a mob last night, but he was still a man. Every mob in every little Southern town is always made up of people you know—doesn’t say much for them, does it? (142)
Jem and Atticus have a difficult conversation following Tom's verdict, and Atticus tells his son that twelve reasonable men allowed "something" to come between themselves and reason on the day of the verdict. He explains that this "something" is the unreasonable act of racism:
There’s nothing more sickening to me than a low-grade white man who’ll take advantage of a Negro’s ignorance. Don’t fool yourselves—it’s all adding up and one of these days we’re going to pay the bill for it. I hope it’s not in you children’s time (201).
Atticus Finch provides some of the most powerful insights in literature. I hope these provide a good starting place for locating more examples of his guidance.