Annie Mitsoda from DoubleBear has been interviewed by one Geraldo Nascimento on his blog. Here's a sample:

How do you organize a thick web of dialog consequences? I imagine that organizing all those stat checks and branching dialog trees must be nerve wracking.

Absolutely! Writing for RPGs with a extensive amount of player choice involves a lot of careful organization, which is one of those things that doesn’t seem like a big deal until you really realize how massive an amount of text your average RPG deals with. One thing we did for AP – that I would recommend to anyone working on dialogue – is we charted out the direction the conversation would take ahead of time. Brian and I would meet up and talk about what each scene was about, what it was trying to achieve, and what the player would want to ask. From there, we distilled the direction of the dialogue into a node structure, and went from there. Tree dialogues – like in SoZ – had a structure that was way more difficult to work out ahead of time, but even jotted notes and charts on notebook paper helped me keep stuff in order.

Aside from the scripting side of setting up dialogues (which I would recommend keeping track of via Excel – I carefully tracked the state of completion for every single dialogue in SoZ that way), I recommend sketching out bare-boned outlines, adding in interesting elements in a quick edit, and then actually attempting to do a solid first pass for readability. Once you’ve got that, try to take a longer view of what you’re trying to do – the flow of the dialogue in the mission, the area, etc. – and run a second pass. Ideally, once you’re on the third, you’ve got the tone of the entire game in mind.