Howdy!
Well, my only online experience with AW has been in Wave, but I've been playing in some other games via more traditional fora. Here are my recommendations:
1) If you can, schedule a regular 'live' session via your instant messaging program of choice or skype if you can swing that. Obviously, one of the draws might be the asynchronous nature of play by post, but you get sooooo much more done in a live chat, and the whole dynamism of interaction and table talk is a lot closer to the real thing
2) Barring that, or in addition to it, in this other game I'm playing, we've used a private message back and forth between GM and player, then post it publicly when it reaches a good chunk of stuff, but our storylines are all pretty independent. For more public storylines, you might just go with a regular forum post format, but I'd a) be super anal about organizing the fora and subfora, and b) establish some pretty clear ground rules about how much you ought to post in a chunk to avoid stepping on any other player or MC toes
3) pretty minor, but make a decision about how dice will work. Will people just roll and post their own results, will the MC roll everything and post it, will every roll be linked to some online roller, or what? With a group of established real life friends, this is probably not a big deal, but it'll be good to have everyone on the same page.
4) For supplementary docs like relationship maps, real maps, character portraits, whatever, having some file-hosting space would come in real handy. Maybe google docs? I know some other suggestions have been made in other threads.
5) A wiki can come in handy for presenting character and NPC write ups, details about the world, et cetera, and might be a handy way for you to keep track of fronts and triangles and all that good stuff
I'm sorry my advice here is so vague, but I hope it helps.