Once the group exists, we should decide the circumstances under which it may accept or reject members. The larger the role this group plays in our story, the more we benefit from this. A character from one will be aware of possibly being ejected for a failure while another may be determined to prove he’s worthy to have been accepted. A more established character may be involved in the inner circle or aspire to be. All of this helps us create depth.
Accomplishing deeds in line with the group’s goals may prompt an invitation to join, with possibly repeated recruitment attempts. The organization will need a sales pitch, so decide what benefits they’re offering someone. Is it safety (in numbers), intel, prestige, allies, or better rates of success? Some are material concerns, but there might also be philosophical benefits of a world view strengthened by joining with others of like mind. Is there a problem someone seeks to alleviate by joining? This can be lack of supplies, high failure rate of their own missions, great danger, or anything that being alone in a pursuit exposes oneself to. We’ll have people joining an organization for different reasons, which can also create internal conflict when some are more interested in one aspect than another. We can imagine someone stating that they’re here only for the money while another character scorns them for not supporting the group’s grand vision more.
Existing members can recommend new members, though this may require having their own membership settled; a new member’s recommendation may not carry much weight. This provides an opportunity for conflict if the suggested person behaves poorly and casts a bad light on the guy who vouched for him.
What causes someone to be accepted or rejected? Informal groups often don’t have formal tests, so someone may join on probation of a certain length, and a certain number of missions. They may be assigned to work with one or more people who have responsibility for them, any of them able to give a recommendation to the group’s leaders about membership. During that time, it’s likely that the organization’s secrets will remain unknown to this person, and even upon acceptance, only the inner circle may know certain things.
What happens if candidacy is rejected? This may depend on how quickly this happens and whether the group is benevolent or nefarious. We can see an evil organization killing a failed recruit or sending them on a suicide mission; in the latter case, what if they survive? They may be forced to commit serious crimes and failure results in expulsion or death. A good organization is more likely to let someone walk away peacefully and have tests that amount to matters of character, judgment, and ability to support the group, including following orders. A group intending to physically fight might require skills tests. A supernatural group might need a display of talents.
People will leave an organization for many reasons that we don’t need to invent here. We only need to decide how the group handles departures.
For evil ones, we can make this simple in that exiting means death. This might be a well-kept secret or one visibly demonstrated. This is an easy way to characterize them early in a story, such as showing a minor character earning this fate. It can shed light on why a more important character intends to disappear instead, possibly faking their death. Or maybe the important character tries to kill everyone else in the group, knowing they’ll be hunted forever if they don’t. We can also have their mind erased or a similar act that safeguards the group’s secrets.
With good organizations, such tactics are highly unlikely. Members are free to depart at any time, though they may incur a debt that needs repayment or which the group could waive. If they’re truly valuable, they may be talked into a temporary departure, but informal groups likely aren’t insisting that someone’s decision is irreversible.
Regardless of group type, a member may not have been important enough to warrant much concern about their exit. An inner circle member is more likely to face scrutiny. This could include inquiries into their motivation. Loss of life or limbs is a risk to many groups. A member can become disillusioned with the group’s stated goals, or exhibit behavior that goes against it. A change in leadership can result in unwanted changes, especially if it’s a coup. During these, factions might appear, leading to infighting and death. These are some issues to consider when creating a history.