-Meetingwords or google docs are good mediums for collab postings. Realtime editing, so basically send over the links and things can almost "flow" together, though some organization is needed if many folks are on at once.
-Imagery's your friend in portraying stuff like that. Metaphor, blah blah. Unless it's essential I personally end up skimming those things.
-Enough detail to draw the basic shapes and images, while allowing particular important details to stand out. Any more I find not only unnecessary, but sometimes boring. I prefer to get my own mental image of a character as compared to someone desperately trying to get every little detail down.
-Find good writers that seem open, PM them, maybe ask them for a 1x1. Start off in the casual forum and work up.
-There are no early signs. There could be early steps such as pulling together a relatively tight group, but every roleplay worth its salt has looked at the end of the tunnel before turning back to life. Be random (within reason, obviously), keep the OOC active, breathe life, and if you're the GM throw prods around at anyone not keeping up with the intended pace. Don't pester them, but keep them around.
If ya need more, I'm around :)