How do you deal with rude children when they are not yours?

I'll try telling the kids parents of his misbehaving so that they could lecture therir child.

Oh, I have no problem with telling them to "Knock it off!" @TheInvisibleMan . Then I look at the parents (if they're around) and tell them, "Contain your child or I will."

I call the attention of the parents but most of the time ignore them.

I give them the "sphinx look." It's impossible to know what their demons are. " A shape with lion body and the head of a man, A gaze blank and pitiless as the sun, Is moving its slow thighs, while all about it Reel shadows of the indignant desert birds." --W.B. Yeats.

I will try to avoid them. If bad situation happened, I will bluff them. For I think it is no use to talk with their parents.

now this is a tough one. I will go and try to the kid's parent or guardian but that's not always a peaceful route . some parents are defensive.

That's quite difficult, as we can't say anything to them. It depends on the situation on what i do..only ignore i can think

It would depend on one's perception of what defines "rudeness". Unlike adults who are expected to comport themselves in socially acceptable behavior, children's misbehavior does not necessarily mean they are "rude". Often it's their playfulness and curiosity that gets them into trouble in the adult world. We should learn to deal with their "rudeness" at their level. Failing this then tell them you're actually a witch and will boil them alive in a cauldron of hot oil if they continue to misbehave.

I will make them understand in a nice way,if they don't listen I will ignore them , because their parents might not like if we scold them. So its better not to notice them ..