I started writing collaborative work in my dark fanfic days (the fanfic was dark, not the days). Now technically this was role playing, rather than fanfic, so this may not apply to other people’s experiences, etc, etc. However, in the group where I was involved, there was a standard collaboration method.
1) You and your co-writer would go into instant messaging or a private chat room.
2) You would each write out your character’s dialogue, along with whatever reactions they were having. “He lit a cigarette. Damn things. But it was compulsive. ‘No, I’ve never thought about going into command. Why do you ask?’ He struggled to keep his voice light. He surveyed the room, checking to see if their conversation had been overheard.”
3) Your partner does the same. “She coughed after inhaling the annoying ensign’s smoke. ‘Do you have to smoke that?’ she asked, waving it away. ‘I’m sure it’s not allowed in here. Anyway, my point is–I heard there’s an opening for a weapon’s specialist on the bridge.’ She leaned forward, giving him a significant look.”
3) This goes on for pages, and pages, and pages.
4) You mash it all up into one unreadable mess.
5) The good taste fairies cry.
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