We'd go in distinct turns that in some cases will take place over a whole day of game time, sometimes a single combat round. (Er, not that there'll be combat, since it's a diplomatic mission, right?
) Anyone who doesn't post by some deadline, doesn't do anything noteworthy.
If there's a need for initiative, I'd roll it for each party member and post it up front, and probably assume the enemies all go after your turns. That way, everybody can say what they're doing without waiting for me to post what Enemy #3 is doing. Note that you can take multiple actions in a turn at the cost of each action being at a (actions-1)D penalty, eg. two sword attacks at 4D skill are at 3D each.
Dice: I'll trust people to roll their own and say the result plus what you're doing. Eg. "Bob lunges at the owlbear and whips around to slash it twice. (ROLL: 4D-1D twice: 10, 12; damage 5D twice: 15, 13)" You'd have to wait to see whether it really hits, but you'd have told me the damage roll in advance.
Creating a mage: the obvious way is to do Sorcerer, 4D Wits and 2D Magic, which gets you four spells plus Sense Weave... but note that many spells don't use Wits.
General rules: say what you're doing, and any OOC questions or actions. You're free to coordinate with other players and edit posts up until I respond.