On his blog, BSG co-exec producer Mark Verheiden reveals some insights into the process of writing for Battlestar Galactica:
There's been some discussion in the ether about how shows evolve, occasionally punctuated with the criticism that the writers and producers are "making it up as they go." That meme strikes me as bizarre. Of course we make it up as we go, that's what writing is all about. In the case of BSG we always had a destination in mind, but there was plenty of room for inspiration and mid-course correction, based on a myriad of factors.
A small case in point occurred during the breaking and writing of the episodes "Oath" and "Blood On The Scales." While writing the script for "The Oath", it struck me that it might be interesting/dramatic if one of our main characters suffered a dramatic set-back in the course of the mutiny. The moment wasn't in the outline, but as I was writing I considered adding a beat where Col. Tigh was shot and badly wounded during the scene when he and Adama confront the Marines escorting them to the brig.
Sometimes on BSG you could just give this sort of thing a try, but blasting a character like Tigh had ramifications for other episodes (obviously), so I checked in with Ron Moore before actually doing it. He understood the impulse to up the tension and to create even more stakes for Adama, but he felt Tigh had been through so much (eyeball gouged out, poisoned own wife, discovered he was a Cylon) that shooting him would have been overkill. But the idea of having one of the final five seriously wounded? That idea stuck...
And so poor Samuel T. Anders wound up being "shot in the cabeza" (as the scene was described in the writer's room) in "Blood On The Scales." And that plot development... well, now we're getting into spoilers for episodes that haven't aired yet.
Read Mark's full post on how stories evolved on BSG.
Mark also notes that the film that he wrote, MY NAME IS BRUCE is now available on DVD and Blu-ray, so check it out.