Of course it's different every time, but this is roughly how I write comics. An idea comes from somewhere. With the Rapid City project, it is usually something that I have faced in my own life. Let's say, for example, I notice how addiction can affect lives.
Then I start thinking about how that idea can be dramatized within the framework of my story. Because it is a superhero story, this usually means a fight. I have to think of ways that this idea can be presented as two different values in opposition. Off the top of my head, it could be something like an enemy turns out to be a former good guy who has gone astray due to an overwhelming addiction.
Now I start to think about how this will work in the comic. Most of my stories are about the character, Kinetic, learning how to be a hero, so this one will likely follow that model. So, what is the lesson he will learn from this encounter? Most likely, I would go with something a little more personal, but for the sake of this exercise I will say the lesson will be "drugs are trouble".
Now I start thinking about how I will lead Kinetic, and my audience, to that lesson. Usually, I work backwards. I think of the scene at the end that I want to get to. In this case it is Kinetic realizing that the man he is fighting used to be a respected hero, but an addiction has changed him.
The next step is plotting in broad strokes. What are the basic things that need to happen to get that scene to happen. I have to introduce Kinetic and his respect for the other hero. Then I have to show that Kinetic does not take this addiction seriously. To keep it in the superhero realm, I am going to say that it is an addiction to some kind of power-enhancement. So, he thinks that the "drug" is not that serious a problem because it has not affected some hero he respects, then he battles some guy, and that guy turns out to be that hero. Lesson learned!
Usually I write all of that in some kind of text document. Either an actual notebook or the text feature of a Celtx project. Very often I will run through this step many times with trouble shooting and making sure it all works.
Once it basically makes sense, I start the tight plotting. I use Celtx's "index cards" for this. For each thing that I know needs to happen, I make a note card. It doesn't really matter what order they are in at this point, as I can move them around. Once I have my tent-poles in place, I start thinking about what I need for each of them. If I know that Kinetic must come into contact with teh positive effects of this drug, then I must put him in a believable (by superhero standards) situation where this could happen. So, what do I need to show to lead up to that? What does the reader need to know in order for each scene to make sense.
In this case I need to show the reader what this stuff is, what it does, and establish Kinetic's opinion of it. Again, using conflict to express ideas works well is superhero comics. In this case I will have a fellow hero invite Kinetic along on a "raid" of some kind to bust people who are making this drug. Kinetic does not participate as the drug only affects those who use it voluntarily. Then a mention of "besides So-and-so uses it, and he's fine."
Still working with the index cards, I make sure that each tent-pole has all of the information and story momentum it needs to stay standing. Usually this is a process of filling in gaps by asking "why?" or what then?". There is a bunch of juggling and rewriting at this stage.
Because it is so focused on events, rather than ideas, this is where the story can run astray. Some really cool thing might logically happen next, but if it does not fit my "effects of addiction" theme, then I scrap it. Or find a way to make it fit. Or put aside for a later date. Reviewing my scenes with the thematic lens often reveals new ways to strengthen the theme and can help to further plug gaps.
About now I have the index cards that will be all of the scenes of my story. Not every card is a whole scene, and not every scene will even make it into the final script. This is my "raw footage" of what must happen.
In the same Celtx project in which I created the note cards, I open another comic book script file, this one I call "scratch pad". This is where I start writing my dialogue. I will usually start with some piece of exposition or conflict that I know needs to get done for the story to move on. With no thought to what is going on around them, I open up the characters and let them talk to eachother. "I think THIS." and "Yeah, well I think THIS!". I leave in all of the "umms" and repetitions and try hard to let the speaker's find their voices.
Once I have the spoken part of the scene so that it leads where I need it to lead, I cut and paste it from the scratch pad over to the issue script where I created the index cards. Celtx automatically turns the index card headings into page headings, so it is easy to drop the dialogue in the right place.
Now in the actual script, I start breaking the rambling conversations into discernible panels. The dialogue gets trimmed and tucked here. If a picture can say it instead, then it gets cut. The action and situation of the scene might suggest other changes as well.
And then it is working it through again and again from top to bottom.
Does the theme make sense? Do the main events express the theme? Are the main events made clear by the individual scenes? What would this character do? How would this other character react? Does it all express and support the theme?
Then there is line editing for clarity, and it's done.