I can only talk about the writing in our game, since that's my part.
Here's what usually happens when I sit down to write:
1) consult our shared design doc, and pick the next piece of content that has to be implemented
2) think up an amazingly vivid scene/dialogue/event that meshes perfectly with it
3) "Yeah, I got this... it's gonna be so cool! Everyone's gonna love it, and their praise will fill the void in my soul!"
4) start to write... get frustrated how poorly it's going... bang head against the wall, repeatedly
5) try to write some more, all why understanding why most writers end up alone, destitute, and suicidal
6) *scribble pentagrams and goat-heads while offering Satan my soul in exchange for some inspiration*
7) get up, start pacing around... curse the gods, Fate, and Dostoevsky for laughing at me
8) get some coffee, play with my cats... get bitten and scratched by said cats... buy their love with some catnip
9) sit down again... more head-banging, this time against the desk! (*desperation noises intensify*)
?) start invoking Cthulhu
?) ??? ??? ??? ::
R'lyeh wgah'nagl fhtagn :: ??? ??? ???
?) finally squeeze out something that's half-way decent and isn't reminiscent of a dumpster fire!
?) save the rough draft, and send it to the rest of the team for critique/review/implementation
?) bask in the warm afterglow... when asked how it turned out so good, reply with "Talent."
And that's why, ladies and gentlemen, no one should ever aspire to become a writer!