Common courtesy

As with all MMORPGs, there are some things that you should and should not do.

* Territory: While no one "owns" territory (it is intellectual property of Wizet), a significant number of MapleStory players grow attached to the area that have been training on for a decent amount of time. This is an "unwritten law" of MapleStory, and it is suggested that you abide by it, if you value your fame level. If you would like to train somewhere, but it has already been taken, then simply change channels. With 19 channels there are plenty of places to train at. If you invade someone's territory, then it is most commonly considered "kill stealing" and will most likely cause arguments. While it is incorrect to say that this is just as wrong to do as, for example, invading a foreign country, it tends to irritate people, so try not to do this. Unfortunately, in some places such as the popular "Pig Beach", territory is very hard to grasp, and a lot of kill stealing occurs as a result.
o The etiquette of territory is hard to define, as everyone has different views of how big their territory is. For some maps, a territory may be less than 1/8 of the map, or even a mere monster. On the other hand, the territory of some maps such as the end of the B3 Subway, and the Zombie maps, extend across the entire map. However, as you train in that particular map for a long amount of time, you will begin to grasp this common, unwritten knowledge. Also if you happen to want to kill say pigs without the random effect of maybe getting defamed go to a really unpopulated map. Say map 20 you will be able to train in relative peace, however you might not be able to kill pigs or anything else fast enough.

* Kill Stealing: Many people "kill steal", especially at earlier levels. In essence, kill stealing is when a person either invades someone else's territory, or when a stronger player follows around a weaker player just to irritate that weak player. Kill stealing is often referred to as "KSing" ("KS" referring to "kill steal", and "KSed" referring to "kill stealed"). Sometimes, a form of kill stealing is used to defend against kill stealing. This situation is rare and cannot be defined with a specific term. It typically happens when someone is kill stealing, is warned, defamed, and still will not leave one's territory. Kill stealing is considered rude behavior and generally results in defaming. The kill stealing etiquette rule does not apply to boss monsters, per global belief. In some extreme cases, one may wait for a boss monster such as Mushmom for a considerable amount of time, and is KSed once it spawns.

* Defaming: Defames, which is the opposite of fame, are generally frowned upon, as they can easily lead to "mass defames" in which a band of people defames a single person repeatedly. Defaming is sometimes a useful tool to use if someone is being extremely disrespectful by kill stealing or otherwise. A "defame war" is similar to a mass defaming, except two parties of people defame each other.
http://strategywiki.org/wiki/MapleStory/Beginner_Guide