Social Norms

1. Atticus most likely follows personal norms. He doesn't rely on other people's expectations. He knows the rules or what is implicit. But Atticus refuses the follow them. For example, he knew the people who worked with him in the case with Tom Robinson didn't want to associate with Negroes in a kind way. This rule probably wasn't really mentioned aloud or in text, and instead probably obvious to most anyway because of the whites' racism towards blacks. He made up his own rules and acted upon what was true to him, by standing up to Tom Robinson. Overall, Atticus is independent and doesn't worry about these rules.

2. An example of an implicit norm that a character hasn't followed was how nobody told Jem not to damage any of Mrs. Dubose's belongings, but instead be calm (the rule wasn't specific). Even though Jem knew deep inside that the idea of damaging Mrs. Dubose's bushes was morally wrong, he did it anyway. Again, the rule was just to be calm, not stating any more about what not to do. In the end, Jem regretted his action because his "punishment" was to read to her.
Another example is how Scout confronted her cousin Francis and said random curse words, and realized shortly after that they don't make sense to her. With the fact that nobody told her to be mean like that toward family members, Scout did so despite knowing that it's wrong deep, deep down. After that action, Scout was forced to be sent home with Jem and Atticus.
A third example is how Mrs. Dubose knew that this morphine addiction she had was wrong; nobody else told her about it, though. The outcome was how she had fought to overcome this addiction.