Some thoughts:
a. when some one is yelling at you, lower your voice. Its hard to talk loud when the other person is so quiet you can't hear them.
b. don't speak passively. wusses shouldn't GM.
c. what' going on in the game when the talk-fest goes on. Obviously something where everybody wants to do something. If its combat, the solution is inherent (you're supposed to take turns in combat, its called init). A good idea is to roll init very early, right when the PCs see the enemy. At this point, they're locked into the init cycle and can't compete for trying to shoot the orc first.
d. make sure your house rules document covers talking in turn. Mine does.
e. either make being bad painful, or make being good worth it. That means, do not listen to people who's turn it isn't and make it clear that you are ignoring them. Come up with a practical punishment system if need be (XP penalties, debris damage, random encounters from all the noise). Make it obvious that disorderly behavior results in bad things happening. XP penalties are usually the best because they don't interfere with the actual game. By making it hurt to be bad, the good players are effectively rewarded.
f. As GM, you control who sits at your table. If they're a problem, talk to them. If they're still a problem, get rid of them. There are far more players than GMs. If you're a good GM, you'll have no shortage of players.
g. I'm not sure what you were talking about with players having to make characters and needing a week or something. It takes an hour, 2 tops to make a character. It's been that way in every edition of every game system I've ever played. Even Travellers. This sounds more like some lame excuse for somebody not being ready. If they're really that slow, restrict them to just the PH. It can't take more than 2 hours to make a PC with just the PH. If their characters are weak, unburden them with survival of the fittest. Monsters always attack the weak.
Janx