A Game of Thrones
How we cite our quotes:
Just thinking it made her feel a strange fluttering inside, even though they were not to marry for years and years. Sansa did not really know Joffrey yet, but she was already in love with him. (16 Sansa 1.8)
While most characters in A Game of Thrones live by the principles of duty and honor, there are definitely other ways of life. For instance, Sansa's guide isn't any knightly notion of honor (keeping your word, protecting the innocent), but a romantic notion of a woman's role: to be a sweet person and to fall in love. We may not agree with her, but these are her principles.
"The Red Keep shelters two sorts of people, Lord Eddard," Varys said. "Those who are loyal to the realm, and those who are loyal only to themselves." (31 Eddard 7.137)
Here, Varys lays out the two principles that guide most political people in the capital: either they want to help the realm or they want to help themselves. These are pretty broad brushstrokes, but Varys seems to be right.
"Back at the inn, you and Chiggen helped take me captive. Why? The others saw it as their duty, for the honor of the lords they served, but not you two. You had no lord, no duty, and precious little honor, so why trouble to involve yourselves?" (43 Tyrion 6.17)
Other people act according to principle (duty, honor, etc.), but mercenaries like Bronn only act for money.