For anyone who has written such a thing, what would you say are some general rules of thumb for writing organizations set up and funded by the government of a major world power (like the U.S.) that's kept a secret from the general populace?
Well, there are tons of real life secret organizations that you could look up. I based the secret gov. assassins from one of my stories off the Japanese Kempeitai, which was sort of a secret police for ww2 era japan. For me, the organization I wrote was not necessarily secret, just that nobody knew who was funding them or what they were up to. My research has shown that most of these 'secret organizations' usually have highly complex and volatile power struggles, often leading to the organization acting outside of the control of its backer. This was kind of a rant, hopefully something in here was helpful!
Well if there are secret organizations out there we don't know how they work because well, they're secret. But I think the most important thing in writing is to give this secret organization real limits. There's no such thing as an all-powerful "secret" organization (except the Illuminati, of course XD), so you have to make sure you don't make them TOO powerful. If a major world power was funding it, they'd have to make it so extremely undetectable that no one could trace it back to them. If someone were to trace it back to a major government, that would be a huge problem for the organization and international politics. A war might even break out. So the way to keep it truly secret is to have it move on a small scale with few members, and maybe only ONE guy with connections to the public government. Those are my two cents.