If you would start a secret society, what would be the aim of your society?
Empowering and equipping members with the tools, knowledge, and support system necessary to take control and create the lives they desire for themselves. Beyond that, projects and initiatives to improve and strengthen the communities in which they live.
It would not be an esoteric order. It would be mostly secular with some philosophical components, but not spiritual or magical. It would also not be about domination. It would focus on balance.
What would be the secret about?
The body of knowledge itself (mentioned above). A set of virtues and qualities each member strives to incorporate into their lives.
It's important to note, that very little of the knowledge is a secret in the sense that it is some unknown thing kept from the rest of the world. Rather, it is several components culminated into a framework that is the secret.
Membership roster, organization structure, etc. would obviously be a secret. The groups existence itself..... more or less a secret.
How would you attract new members and based on what criteria would you select members?
Typically, there is a protocol where a candidate is proposed, reviewed, and voted on before ever making the candidate aware (what's the point of approaching the candidate if they're not approved?). If approved, the candidate would be approached and invited to join.
Although, there are plenty of exceptions allowing people to "find" the group in order to be considered.
How should your society be organized, ex. should it be centralized or decentralized, online or real life?
Founder appoints a high council to run the organization globally, but does not get to vote on matters. Membership is organized into chapters at local levels with district and regional representation. Regional directors make up the low council. Healthy dose of autonomy for chapters, but must still follow edicts and guidelines set forth by the council (It's basically a franchise).
Members follow a tiered progression (basically degrees). Each degree has requirements to be met before a member can progress. Most people prefer the benefit of real life interaction, however it's actually not required. Plenty of virtual stuff and "at-large" members, but attending a meeting in person is required at least 4 times a year if there is close proximity to an established chapter. Totally possible for introverts.
Should there be a custom letter or similar to encrypt communication?
Each degree provides a certain amount of "lore" and symbolism. That's as much as can be said about that here.
How much it would cost and how much effort it would take to maintain it?
$10 a month to be a member. Effort is up to each member. You get out what you put in, or in other words, your experience is what you make it. You could pay the dues, attend the meetings, and never progress if you wanted to. But, to be in good standing, you have to at least pay the dues.
This are all question you would likely face already in the beginning.
But do these questions distract you?, or would you try it anyway?
What are your thoughts? would you start a new society or would prefer to join existing one?
I would try it anyway. In fact, I have. If you have questions, DM me.
