QUOTE(juice @ Jun 22 2008, 08:20 AM)

Use your microphone to announce to the team that you are new to comming and need guidance but you're willing to work with the team and learn. They will take it from there, to a win or a loss.
Well that's kind of more of an actual action rather than knowing something...
But yeah that's true. In fact, sometimes it's good to do that even if you kind of know how to command but are up against a competent alien team. The only problem with doing that is your will have your odd individual griefer/whinner or thinks-they-know-it-all-but-don't/won't-shut-up-ever, but it's almost always worth it. Plus there's another benefit, if you take the advice of your team and communicate, they won't blame you as much if your team looses.
I would say the number one thing any new commander needs to know would be your top two priorities in order to win.
First Priority:
Kill the alien team completely & permanently
(this means destroying their spawn(s) and then hunting down any survivors)
Second Priority:
Deny, acquire, and hold resource nodes
(so you can gain a tech edge on the enemy so you can complete the first priority)
And for the newbies who may read this:
Deny means destroying enemy resource towers
(The only thing worse than your team having few resources is the other team having more)
Acquire means building your team's resource towers
(You must get resources, period. Failing to do so early and consistently will make the game exponentially harder to win)
Hold means defending your team's resource towers from enemy attacks
(It's inefficient and wasteful of time and resources to have to rebuild)
Often people think that the main objective is grabbing resources. Actually it's technically not. Don't misunderstand me, it
is important, but more important is
destroying the enemy spawns. That's why blitz tactics are so often overlooked, people are only thinking about "tech-ing up" and not the primary goal in order to win. If the enemy isn't expecting it and you can take out their ability to spawn... gather an assault and go for it. That's usually checkmate right there.