What kind of behavior is consider assertive?

One example is telling the waitress to have your steak redone, when it did not come out as ordered.

Laughing. I LIKE that one, Phoenix. I guess another would be taking up the issue of a grade with a professor.

When the Starbucks people give me my Iced Caramel Macchiato, without the caramel, or with too many shots of espresso, or whatever it is they do to screw up the deliciousness but make it taste like revolting, bitter-tasting poison, and I come up to them and tell them they screwed up and I want a new one. And I get one.