Remember to shake your opponent's hand before each Match and say your name. It is important to have good manners in a Duel, just like in the rest of life.
If you are winning a Duel, be nice to your opponent. Nobody likes it when they lose a Duel and their opponent is mean to them too. Think of how you feel when you lose a Duel. Maybe your opponent would like some tips from you on how to improve his/her Deck.
Remember to be polite to your opponents, and everybody will have more fun Dueling. And you will make more friends, too!