One of the first opinions that originally came from Atticus was what Scout says in chapter 2 about the Cunningham family. She says that they don't take anything from anyone unless they know they can pay them back. She said that "they never took anything off of anybody, they get along on what they have." She learned that from Atticus when she found Mr. Cunningham bringing different food items and firewood to pay him for his services.
In chapter 3, Atticus tells Scout that in order to understand others, she had to "climb into his skin and walk around in it." Scout tries to do this with Miss Caroline to understand her better, and she does it with the Ewells when trying to figure out why they get to hunt and trap out of season.
Then in chapter 7 Scout once again tries to use this rule to understand Jem and why he wouldn't talk to her after he brought back his pants when he lost them at the Radley fence. In the same chapter, Jem has the idea of writing a thank you note to the person leaving them gifts. That sounds like something Atticus would suggest, so that could also be considered Atticus' influence.