Reposting.
The biggest challenge in organization is organizing itself. Cell theory is your greatest friend here; find yourself two buddies whom you would trust with your balls and have them recruit others that you do not know about specifically, all with code names, and cell numbers and letters.
From there, the person below them recruits two more that only they know about (and do not share with people above them or in the same cell letter) and take and pass along orders from the executive cell, you and your buddies. If needed, it may be necessary to give the codename and contact of one man in amongst the neighboring cells to both circumvent damage (traitors and raids).
Messages go back and forth from these lines, with each cell passing along a message to their superior until it reaches you and your two buddies, with a signature on the message giving the path which the message took, enabling you to tell where damage has happened in your organization. The most important thing here is that nobody knows who exactly is in the organization.
Let's say you have an organization of 81 people, four layers including executive. Your orders are to fuck up this government building that happens to contain a whole bunch of people deciding guns are only for the elites, peasant. The orders go down the chain from cell A, the executive cell, to cell D, the guys on the ground nearest the target. But there's a traitor in cell c-3- operative two- he's a loyalist. He gets the two men he knows complicit arrested and attempts to get the squads under him arrested. Squads c1, c2, c4 immediately know about this by the squads under them reporting that their neighboring squad has not received an order in the last 72 hours, a telltale sign that the commanding squad above them has been compromised. This also works in reverse; a squad-D5 member reports that he found cruicial information to pass up to executive immediately, and he and his squadmates pass it along to their respective cell leaders above them, and if they can't get them, report to their neighbor that they have no contact with their leader in C block and need to pass information to executive. This ensures the message gets through, as damage can be reported immediately, and can also be used to sniff out people trying to fuck with a message, as deviant messages can be traced specifically to organization block and unit number via message signature (layered PGP is a good example of this). This simple system ensures participation and minimization of risk for everyone involved, as you cannot be forced to divulge anything about the organization that you do not know (as you only know the code-name and contact details for one man above you, and one man beside you in your cell block). Obviously, you MUST ensure you have encrypted channels to run your revolution, else all of this is for naught.
