Almost all greenskin races are tribal, gathering in bands for mutual support and protection. Loyalty to one's tribe is almost inborn, as a survival instinct. Strife does often break out between greenskin tribes, over territory, resources or just disagreements, but generally a greenskin tribe will side with another tribe against the "fairer" races such as humans, dwarves or elves.
The tribal leader is often called the Chief or the Warchief, though there have been occasions where a particularly large and powerful tribe will proclaim their leader a king. Leaders must show strength, will and aggression and be always seeking to better the standing of their band, or they will surely be challenged for leadership, which usually involves a fight to the death. Even though the greenskins often fight and act rude, the chain of command is clear in a tribe. In a greenskin tribe, the greenskin wear their rank like a badge of honor. Higher ranked greenskins will often take advantage of the lower ranked ones, since it is expected of them to follow all and any orders given by a higher ranked member.
Slaves are viewed as possessions of great worth, as is gold, silver, weapons and armor. Greenskins often take trophies from their kills and wear them to display their dominance, often through charms and jewelry, sometimes even making armor or something else that could be useful for them.
The strong rule over the weak more often than not, and while females and children are viewed as property they are also protected and valued, but rarely shown much respect or affection, as greenskins know the world as a harsh place with no room for weakness. There are greenskin females who have chosen the path of the hunter or the warrior, and while those are rare the few who have committed themselves to that path are more than capable of taking on a greenskin male if provoked enough.
Greenskins are driven to conquer. They are driven to dominate. They are driven to take what they want in any way they can. It is a way of life and a way to survive. Their entire cultures are built around strength, prowless and victory in battle. Almost all non-greenskin races are viewed with, at best, suspicion, and usually hatred. Elves and Dwarves are particularly despised and are racial enemies to greenskins. Orcs harbor a great and abiding hatred for elves, and even their gods are said to have battled one another in the very beginnings of time.
The Common Bond
There are only a few different factors which are held in common among the Greenskins. First, is the grudge that spans back so many centuries that most don't even know how it all started - the hatred towards humanity and elven kind. Both sides are often found blaming the other; in the eyes of most greenskins a human or an elf is a weak, pathetic being, often referred to as "vermin". They question their lack of familiarity against the members of their own "tribes" (villages etc.) and frown upon their false gods. Humans and elves on the other hand often view greenskins as savage beasts without religion or culture, driven by the desire to conquer, pillage and kill.
All greenskins fiercely defend what they consider theirs, be it actual land or just their possessions. As such duels are often fought over such things as good pieces of meat, weapons, pieces of armor, even ranking (including tribe leadership) or respect - basically any time a greenskin wants to take something from another greenskin it leads to a fight for it. Challenges can be done to first blood, first to get knocked out, or even who can hold the most alcohol. It is VERY rare for greenskins to actually duel to the death or twice about the same thing, and if that happens it usually involves trying to claim a leadership position within a tribe or to take away another greenskins rights to land.
Unfortunately, for those that trespass on greenskin land, any time an interloper enters greenskin territory without an invitation it is considered an act of aggression. It can be answered with the unknowing visitor being battled, captured or in the worst case killed.
Greenskins are tribal in nature and as such require the help of the tribe shaman to incite the spirits of animals, or their ancestors in every day life. Every tribe has its Oracle, a spiritual leader that serves as the head of the spellcasters and an advisors for the tribe and the Warchief on all mystical matters. Rituals play an important part in a tribe, and they are often preformed to initiate new members, celebrate religious feasts, prepare for a battle or a war or simply strengthen the tribe spirit. All of these events need a shaman or an oracle there to call upon the spirits to bless the greenskins and give them strength. Shaman hold a special place in greenskin culture as they are both revered as the messengers of the spirits and as such can control powerful ancient magics.
Many greenskins fear magic users in general, as magic is considered to be something deceptive that shouldn't be trusted. Therefor shamans, warlocks and others magic users are often outsiders in a tribe, which is also why they tend to form special orders of their own within their tribes. While most shamans and warlocks are "normal", a lifetime of channeling spirits or demonic energies will take its toll, and many lose themselves to insanity as they get older.
But no matter the occasion, if a group of greenskins are gathering for anything of importance there is usually a shaman in the heart of the group. Their mere presence is more than enough to make greenskins fight until they die for fear that the spirits will punish their cowardice.
All the realm should see the Greenskins as a mighty foe, one to be reckoned with and respected not only by their absolute strength and ability in battle but by the loyalty and honor portrayed amongst the tribe's brothers and sisters. Honor is given to those who earn and deserve it, honor thy brother and sister but do not honor the cowering fool that has just finished calling you a stupid mule. The nature of a Greenskin is to gain honor by serving their tribe, either through victory in battle, expanding the territory, populating the tribe with capable warriors or anything else that will strengthen their family.
A greenskin will serve their tribe until their last breath. For a greenskin the tribe comes before everything else, and it's considered a honor and a duty to protect their kin against other races. A greenskin doesn't fear death, and if one should fall in battle protecting their kin or their tribe, their memory will be honored by the other greenskins as a brave and honorable warrior.