Social contract

If you play RPGs I bet you had those sessions where everyone were on the roll. You had fun, you understood one another without words. It was simply awesome.
And then - there were those sessions which were ruined due to the lack of agreement - and I'm not talking about determining whether your character is in the room or not.

Those sessions where this one, single player ruined the fun for everyone by arguing he should be able to pull out a lightsaber in the medieval setting... or that one session when everyone decided NOT to kill that NPC* after a very emotional and heartbreaking scene and THAT SINGLE PLAYER killed the NPC anyway "because my character would do it anyway" without any reasons whatsoever (usually code for: "meh, why not"). Or that situation when the party seeks an audience before a noble and THIS SINGLE PLAYER acts like "eee, what's up, doc". Or someone who sets fire for the city "for the lulz, lol. Chaos, man, chaos and entropy."

You know. THAT SINGLE PLAYER.

Or maybe - if you play with more than one group or sub-groups - there are some teams you know you will be on the same page whatever happens and teams where you never really have this much fun...

Fun fact: that player might have honestly played with the best of his abilities and intentions and did not know the others will not appreciate it.

Basics

Role playing is a group activity.
You may say it's' obvious, but we often tend to overlook obvious things.
Each group has a set of rules regulating behaviors and determining what is acceptable or not. You also have one, even if you have never really formalized it.
Such a set of rules is called "social contract".

What is social contract?
There are several definitions, but going after one from Jean-Jacques Rousseau, social contract attempts to address a following problem: "How can we be free and live together?" Without going deep into philosophical dispute and adjusting it to RPG context, social contract attempts to determine the set of rules for a fairly small group (players) that will allow them to have fun without hurting other group members in any way.

Content

What is in your social contract?
Those are things like:
"We do not step out of the setting/convention unless we all agreed to play comedy / absurd system." or
"We do not touch topics of race / religion / taboo during sessions." or
"We do come for sessions on time." or
"When in doubt, even in non-directly game-related topics, game master decides." or
"Smoking in playing room is (not) allowed." but also
"We do allow some eroticism, but do not accept outright pornography." or
"We do not play evil characters."

Basically, this is your code of conduct for game and game-related situations.

What's in it for me?

Do you really have to explicitly state your social contract?
Not necessarily.

If you know people you play with and you know one another, you will probably be fine without explicit definition of the contract - by now you probably have one without even knowing it.
Did you ever have a new player enter your group? Was there any culture shock? Bonus points if they were an experienced player, used to very different set of rules and actions in a RPG game.

So if you play in the same group a lot, you have your own social contract, even if unstated. However, the more heterogeneous group, the more differing cultures and experiences are involved, the bigger the need for stating even the most obvious things. For example, imagine playing with a devout believer of any kind of religion and - not even knowingly - desecrating their holy symbols. Not the situation you want to end up with, do you?

But you don't have to reach that far. Differences in education, in wealth level... all this can affect how you will work as a group.

Defining

How can you define your social contract and what will it be like?
Your social contract will be affected by things mentioned above.
How to start building it?
One of the ways is to ask your group what will not be acceptable for them, and which areas to avoid.
You may inquire about religion / cults / eroticism / fears.

And, for everything holy there is, if your fellow player tells you 'no spiders', do remember! Neither the player can make a druid with spider companion, nor the GM can use cave spiders as opponents. You don't want to scare someone with arachnophobia to death!

Also, remember, that your social contract is not something set in stone. Once your group learns to cooperate and trust each other, you may want to waive some parts of social contract, or experiment with introducing something that was a "no-no" earlier. However, only with consent of everyone present!

Be aware social contract is negotiated and it is a compromise.
Everyone has their own set of expectations, and not all expectations are compatible.
This means, that in worst case you may not be able to come to agreement - but to be honest I'd rather find that out during a discussion than during an actual, on-going session with heightened emotions.
This compromise also means that in diverse group noone will be completely happy. But at least the group agrees on something and either they will comply (with the deviations from the contract easy to point out) or they have a choice not to play in this group. In both cases, they do know what to expect, though.

The danger is that the shy members of the group may not speak or even if they do, their opinions and thoughts may get disregarded by the vocal ones. But this is a completely different topic. It is in your best interest - regardless if you are a GM or not - to encourage those shy people to speak up.

Enforcement

All nice and fine, after a heated discussion your group agreed on a common social contract and all was fine until one of the players started to break it. Or maybe someone new joined, accepting the rules, but is now ignoring them.
What can you do?
You have several tools.
First thing, talk to them. It can be as simple as "The fact that your character burned down the chapel for no reason at all was very disturbing for me / John / Jane. Please, do not do that again."
Second thing, you can embed some parts of social contract execution is the in-game world. One of the characters keeps avoiding to pay, stealing and offending every single NPC he/she meets? Put a bounty on his / her head. Might be an interesting session, but might also teach offender a lesson.
Finally, if nothing really helps, you may have to - however harsh it seems - stop playing with that person.
You don't have to go all "You evil XYZ, we don't want to know you any more". You can still be friends, just not doing this particular thing together. We do have a friend, whom we really like, but we'd rather not play an RPG session with that person, as chaos "for the lulz" is not what we find entertaining.

Summary

Social contract can be a very helpful tool for you to understand how your team works and what are their expectations when it comes to role playing. It can also help you weed out some ideas for the sessions that would turn out to be unacceptable by some group members - after all we all want to have fun, not be offended in any way.

There are different ways to enforce social contract. Most often you can clarify situation by simple discussion if any violations happen. Your final weapon is excluding offending player from your small RPG society, but this should be used only in hopeless cases.

In fact, social contract is a tool not just for gaming, it can come handy for any team situation.


(*) NPC - non-player character