In Character Customs
Below is a list of in character customs of which players may not be aware. This is not a comprehensive list, but these are the most important to know.
Gift Exchange and Refusing Three Times: It is customary in Rokugani culture to exchange gifts to mark meaningful moments, diplomatic events, and show gratitude. What it is unusual about this practice is that it is customary for the recipient to refuse THREE times before they accept the present. The purpose of this custom is allow the giver to show his sincerity and for both party to pay one another compliments. However some parties use this custom as a method of sharing cloaked insults. There are exceptions to custom such as emergencies or insignificant acts and items. The rule of thumb is that if the gift is significant, there is no rush on the exchange, and the gift is being given directly to the intended recipient (as opposed to a messenger, servant, etc.), then the custom should be observed.
Saying Something without Saying Anything: Given the pressures dealing with reality of Court and the reality of outside world, a custom has grown up that allows samurai to exchange ideas, rumors, and points of view without having to be accountable for them. If a samurai covers his mouth while speaking (typically using a fan, but a sleeve with do if one is not on hand), what he said was never said as far as the Court was concerned. To use an extreme example, suppose a Scorpion courtier walked up to a Lion host, covered his mouth with a red fan, and told him that he will poison his first born son. The Lion would not be able to act directly on that information. He could not go to a magistrate and have him arrested based on his testimony. If he struck him down in open his actions would probably be considered unjustified and he would executed for murder and shame his family. However the Lion can still react to the information. As a host he could turn his guest out for the slightest reason and none at all if he is willing to suffer a reputation of being a bit of a poor host. He could immediately order a group of samurai to follow the Scorpion around for his protection and confine him to his quarters for his protection (effectively putting him under arrest). He could have his son moved to somewhere that is safer or call a Shugenja to heal him. Basically anything that is already within his right to do if never knew the Scorpion was going to poison the child, he can do. This tradition does not hold for peasantry.
Dueling: Dueling should not be seen as a short cut to getting ones way all the time. Dueling is a means of settling disputes between confrontational parties. The dueling tradition is a natural result of adhering to the Celestial Hierarchy. In the Celestial Hierarchy, a being is not right because he is powerful, he is powerful because he is right. Admittedly this system breaks down in the earthly realm, but to deny this truth is acknowledge that the Heavens are not on your side. In the ideal system, when two parties of roughly the same status duel, the righteousness of their decision will show through and they will win the duel. Thus dueling is used to determine who is in the right and who is in the wrong. It is not used to force someone to behave in a certain way or surrender their natural rights and privileges. Now in the process of determining who is right and wrong, it may be determined that the wronged party is due restitution. So to use an example, a Kakita duelist could challenge the Lion general on the grounds that his invasion of Crane lands is unjustified. If the duel is accepted and the Lion loses he made be made to remove his armies from those lands and tribute be given to compensate the losses of the Crane. The Crane duelist could probably not demand that the Lion surrender his army for execution or serve him.
A person can not ask just anyone to a duel to settle a dispute. A person who is clearly superior to the individual can refuse a duel with no loss of glory or honor, and if the difference is large enough the challenger might actually lose glory and honor. The below rules of thumb are not absolutes and do necessarily apply to duels for entertainment or practice (such duels are always intended to be non-lethal):
Trade with Gaijin: To put is simply trade with foreigners is illegal. It occurs of course, but one takes a risk when doing so.
Firearms & Explosives: Firearms and Explosives are illegal. Only few individuals are even allowed to handle fireworks.