Michael Avon Oeming's interview with Warren Ellis is good on Ellis's methods and aims with comics. Excerpts:
M: I think too many comic writers never really think about the craft, they just keep writing and stumble their way out of crappiness – if ever at all. I found a little bit of studying the craft took me a long way, and I still dissect it as much as possible. What was the first "rule” or guideline you learned about writing?
W: Hm. You have to remember that a lot of us Brits learned to write comics from a single example: one page of JUDGE DREDD script reprinted in a 2000AD annual around 1980. Me and Garth Ennis still laugh about it. And we both still write scripts in something approaching that form. Around '88, someone told me the Stan Lee rule – 28(ish) words per panel. An average panel on an average page can't usefully hold more than 28 words of dialogue and/or caption. I do that by eye, now – if a single balloon or caption runs into a third line on the script page, it's starting to run too long.
I'm still learning, all the time. The thing I tell people is that you don't learn how to write comics by reading comics. You learn how to write by reading books. You learn how to write comics by *dissecting* comics. You need to cut into the page and discover exactly what tools the creators employed to attain an effect. [...]
M: I like to build my scripts from the ground up. Do you do anything like this, or do you find you can just jump right into it at this point?
W: I'm the most arse-backwards writer in the business. I've been known to start with a scene somewhere in the middle with no characters or setting and build in both directions. I usually start with a bunch of random notes, connect them up and go from there. Technically, I'm one-draft, but I edit as I go. It goes down as dialogue and brief directions, raw, and I take another pass at everything when I go back and format it into script. Most often, I go into something already knowing the themes – it begins with something I want to talk about, and everything follows from that. I tend to feel character arcs are part and parcel of the writing process – it's not a separate step; it's just something that happens if your story's working. Or, sometimes, not – I don't consider "the growth/change of a character" crucial to a good story. Sherlock Holmes maybe had two elements of character development in his entire career.
M: Do you keep the artist in mind when writing, if at all?
W: Constantly. I'm living with the script for a week. The artist is living with it for a month. It needs to be tailored to them, and it needs to show them off at their absolute best. I'll read tons of their work beforehand, look for what they do well, look for the things they haven't gotten to do and the unrealised potential therein, and go into it trying to make them look as good as possible.