Just put together teams such that one won't have a great advantage over the other(s), decide on how you want the game to run (time limit on days?  majority/plurality lynch? punishment for lurking? etc.), and make sure people follow it.  Warnings and modkills are really your only tools so you have to use them wisely. 

Flavor isn't necessary.  Obviously it can be screwed up if you aren't careful and ruin an otherwise completely balanced game.  (Fortunately for me, the deputy immediately getting lynched combined with the cop ... being radishhead ... counterbalanced the flavor meta disadvantage mafia were faced with due to my mistake.)  So don't feel like you're obligated have to have a game with flavor. 

On the other hand, if you want to do flavor, go for it.  Just make absolutely sure people can't use the flavor to scumhunt in any way.  If you want help with balancing the teams, or anything else, find someone to help you (they probably won't be able to play since you'll probably be giving them lots of info about the setup that players shouldn't know ... unless you go with an "open setup" where the roles that are in the game are public info).  You can also have a "co-mod" who can be in the thread while you aren't, doing official votals etc. 

So how do hosts assign roles and stuff? I have read it is random, but how do you do that random? Is alignment random as well?

:O Come again?

Come again what?

Please, you'll end up almost like Radish - who I'm lead to believe is so bad he is good - except you wont have *quite* reached full circle yet ;)

Our very own Peh-zus is from Ísland

Ah, ok. I may have to ask him a few questions at a later date as to what kind of clothing etc. I should bring haha ><