Well, I don't really think there are established rules per se. We've been rotating the GM between Jim (Roy Hinkley), myself(Tristiepr), and Sarah (Phlu) to give everybody a chance to play. If you know how to, you can roll your own character (we've been using classic Traveller Book 4 Mercenary), and have myself or Jim look it over. That's about it, we try to be pretty open to allow fun gameplay. We've been mostly running off of Classic Traveller, but we have adapted to a different combat system we found, if you join the campaign it's a handout labeled "Combat System C".