Best Practices for Threads and Groups?
I don't play Traveller, and don't know much about it beyond the name, but when it comes to threads, there are a couple of common practices I've noticed.
First off, like the others have said, have game-related, informational threads. Stuff like Character Generation and RTJ Info can be notices, and closed, because you're the only one who ever needs to post in them. OOC threads are great...some GMs don't like them because they want everything in the game to remain game-oriented, but I got into gaming in no small measure as a social interaction. Some people play bridge, or cribbage, or even poker...I roleplay. And an OOC thread gives players like me a place to get a little better acquainted with just who's sitting around the virtual table. So, yeah...I'll second (or third) everything they've said on that score.
With regards to organizing your in-game threads...that depends on how you want to organize your game, in general. Some games I'm in have the threads done chronologically...when this particular 'scene' is done, a new thread comes up and the game continues there. If you want the game to 'read' as a story or a novel, this is an easy way to facilitate that. Other games I'm playing have threads for various locations, which is convenient if you have multiple players who may or may not be in scenes together or who move around a lot...a thread for a ship's bridge, cargo hold, engine room, etc. This does make things more difficult to follow for people who may join the game later and are trying to read up on past events, because players don't always indicate which thread (and which post) contains the continuation of what they're doing...but if you want your game to have more of a 'day in the life' feeling for people playing it, this makes it really easy (you can swing by the hangar deck and check out the shuttle, pause on the Recreation Deck on your way to Medical, and then go back to Officers' Quarters to sleep off whatever medication you got before you go to the Bridge for your duty shift...each one being in a separate thread, which may or may not have other players active at the time so the chances for random, or 'random' character interaction are good, as opposed to the more regulated feeling of scene/chapter-based threads where everyone is expected to be there together...)
It's all a matter of your personal preference. The one game I run is episodic by design, so my threads are done as episodes (apropos, as it's based on Robotech...) But even then, I inherited the game from another GM, and it was already established as such when I took the reins...and I had no interest in changing it. If I was running a game where everything happened aboard a single ship...or even a couple of them...I'd probably do my threads based on locations, rather than events.
As for groups...that is ENTIRELY up to you. I've been in games where everyone was in the same group (in terms of RPOL access...Group 0), so we could all see what everyone else was doing. I've also been in games where each team was in its own group, so nobody could see what they were doing (since you wouldn't have any idea in a real-world equivalent situation). Been in games where each ship was its own group. The benefit to having everyone in the same group is also the drawback, depending on how you look at it. It's beneficial, in that everyone gets a feel that the game is moving forward, even when your specific team isn't doing a whole lot at the moment...but the drawback is, it can get difficult to keep track of what your specific team is doing when you're, say, an infantry team on the ground, trying to infiltrate a building, and the thread is getting cluttered with posts from the air support talking about their dogfights and the orbital support talking about planetary bombardment actions. However, everybody knows that SOMEBODY is still working on the objective of the mission, so it serve as incentive to keep going with your part, as well...
That one, you might want to confer with your players and see how private they want the various points of the game to be. Since you can see everything, as GM, it won't impact you that much, individually, but it will heavily influence how your players experience the game.