I have an example of someone being rude. There's this guy in my math class - when te teacher asks a question, he doesn't just raise his hand to answer - he waves it around. Or, he calls out the answer. He just wants to make a good impression on the teacher, but the rest of us interpret this as inappropriate, because no one else has a chance to answer. It's good to raise your hand, of couse - but quietly, ya know ?