Part of any society is organizations, groups of people of various sorts.
Humans, at least, seem to have a desire to gather and become associated with each other. Obviously, there are exceptions, but in general this appears to be instinctive. Other sentient species may be different. But, for our purposes we’ll assume they’re similar enough for this post.
So, all fictional worlds have groups, whether official or otherwise. Therefore, we need to know some information about these groups. Which begs the question: what do we need to know?
I think there is a relatively small core of information that we need for groups in our worlds. There can be more, certainly, if we wish to develop more detail, or if the group becomes important to the story, but that’s bonus above the baseline.
Leadership—Who is charge, if anyone? Equally important, how is that person or group chosen? What can that person/group do, or not do?
Ex. A university is run by a president who is chosen through a job search conducted by the board of trustees.
Organization—How is the group organized? Is there a hierarchy or other system of ranks? Is there local, regional, national, or global leadership/organization? Are there sub-groups (e.g. departments)?
Ex. A motorcycle club has ranks of membership and is often set up with local, regional, and national chapters.
Goals—Why does the group exist? What is their purpose?
Ex. The Red Cross exists to provide assistance in disaster and other situations in which medical and supply aid is needed.
Where are they?—Are they purely local, regional, national? Are there any places they frequent? Hangouts? Bases of operations? Types of places they tend to turn up?
Ex. The CIA is based in Langley, VA but maintains field offices in various parts of the world.
Relations with Others—What do they think of other organizations in the setting? Do they interact with any others? Do they have allied groups, enemies, or groups they are (un-)friendly with?
Ex. The KKK really hates the NAACP; the NAACP maintains good relations with the Democratic Party.
What do they do?—Does the group conduct research? Stage protests? Fight others? Educate people? What is it that they do when they gather together?
Ex. The 22nd SAS conducts counter-terrorism and reconnaissance operations in military conflicts, including a wide variety of combat and recon missions.
Who can join?—If someone wants to join this group, can they? What do they have to do or be to join? Is there an entry ritual? Does the group only take certain kinds of people? Why?
Ex. To join Hillel, one must be Jewish, but otherwise simply shows up at a Hillel meeting.
Brief History—How long has the group existed? Has it been involved in any notable historical events? When was the group created? What has it done in the last 10, 50, 100, 300 years?
Ex. The Black Panthers were heavily involved in the Civil Right Movement of the 1960s in the U.S., including a variety of protests and demonstrations.