Let's talk comic scripts, too.
How detailed? how do you write 'em? What should they look like?
The answer here is trickier, in that there is no right answer. Comic scripts run the range, from Alan Moore's thicker-than-thick scripts that are nearly pieces of literature themselves....to the old Stan Lee scripts to Steve Ditko, where the script was basically a phone conversation that Ditko would then draw, and then Stan Lee would put some words in it.
(You may think I'm simplifying, but I'm not by that much. Early Marvel was pretty much like that, for quite some time.)
Some people fall more or less in the middle.
My answer: Write to your artist. This means that how you write a script will change each and every time.
The advantage to writing a thinner, less detailed script is that you're giving your story, you're giving the tone and idea of the comic...and then you're letting the artist really be inventive and creative with the visuals, letting the artist provide the texture and the tone that he gleans from your story. In a way, this is like having the comic drawn by a Beta Reader, if you will, in that if he's drawing a dark and gritty 'tone' to your comic, it's not because you wrote "I want it drawn in a dark and gritty tone," in the script, it's because you wrote a script that's dark and gritty and he's innately picking up on that.
Plus, it means you get surprised when something comes back that's clearly your story, with yoru words, and your ideas...except it's not yours in a lot of ways, and you get to delight and thrill in reading it, as if it were a story written by a soul-twin that you somehow know, without knowing.
...
A piece of advice: Unless important to the story, if an artist returns a result that's a bit different from what you intended and it works, then think carefully before changing it.
When I write, whether it's comic scripts or short stories or novels, I have very clear visuals in my head. WHen I write comic scripts, I can concentrate hard enough and see how the panels look, how the characters look, how the page will be set up, all that. I always know how the characters look in my head.
But sometimes, the artist picks up on details (as I mentioned above) and goes in a little different direction. A key example is, my artist for my robot serial sent me a concept sketch of one of the key characters in the story that looked nothing like I envisioned, but exactly like what I think I meant, under that all. Do you see what I mean? What I saw was different from what distilled onto the page, and that's what he picked up on and drew from. Now at first, it jarred me because my instinctive reaction is "That's not how he looks," but that's a knee-jerk reaction and nothing more. I like how he drew the character, and that's the image that I write to now. I think it writes a stronger character.
Let your artist surprise you, and let yourself be willing to be surprised.
...
Back to comic scripts.
My default method of writing a script is pretty basic. Here's a rough idea:
...
PAGE ONE (nine panels): Three panels on top, one long strip panel, three panels below, two panels below that.
PANEL ONE: A shot of our man walking down the street, hands in his pockets.
NO TEXT.
PANEL TWO: A shot of our man, same as before, but shadowed heavily.
TEXT (People shouting, off-panel): Oh my God! What's THAT!? Look out!
PANEL THREE: Our man looks up, startled.
CLARK(thought): This is how you know the day's going badly.
PANEL FOUR: A robot lands on top of CLARK KENT, scattering bits of road and cars all around it in a heavy, heavy shock wave. We see a bit of John's hand and foot sticking up in the panel, out from under the robot's big feet.
PANEL FIVE: Complete blackness.
CAPTION: "That really hurts. I don't care how invincible you are, big robot landing on top of you equals pain."
PANEL SIX: A side shot of the robot's big leg. It's raised up out of the hole in the ground, CLARK's hands pushing it up. His skin is intact, his sleeves are tattered and filthy.
CAPTION: "And honestly, a big robot? Who wakes up and thinks 'golly, today I will build a big robot, what a great idea.' Seriously?"
PANEL SEVEN: CLARK sitting all the way up, arms over his head, still holding up the robot foot. His teeth are clenched. He's filthy and his clothes are shredded and dirty, but his skin is intact.
CAPTION: "If that's how they think, I don't know why I even need to stop the bad guys and save the world. They aren't getting out their front doors this way."
PANEL EIGHT: A shot from behind CLARK, who is now standing up in the hole. His arms are back, he's just flung the robot off him and despite being six stories tall, it's gone sailing away from him.
CAPTION: "Still, I don't get on the front page of papers by looking good in tights, which is a shame."
PANEL EIGHT: A shot of CLARK'S chest, where he's just ripped open his tattered shirt and jacket, to reveal the SUPERMAN uniform underneath.
CAPTAIN: "Guess I'd better get on with it."
...
Now, maybe when the robot lands, I'd want to provide a little more description about what he looks like. Is it a big blocky foot that lands on Clark Kent, like a Gundam robot or a Transformer? Is it smooth and rounded, like Metallo or an android? Is it white with red trimming? Gray with green trimming?
On the other hand, this is where a good rapport with the artist comes in handy, in that you can casually mention in your e-mails back and forth (and I do mean casually, assuming you two just talk) that your robot's big and green, and here's a DeviantArt picture that you think really looks kinda' sorta' like what you're going for, but not exactly. And then the artist goes "Oh, I get what he means," and goes off and does something cool.
OR, in that same script, I could have detailed every little thing. God knows I have it in my head. I know that when the robot landed, it threw up bits of concrete that punctured the windows of a Taxi Cab, that at the edge of that long panel was a man in a brown suit ducking, with his briefcase held over his head, against which deflected a small chunk of concrete, and in the background is a woman running away between tall buildings, and a street light that's red.
But what's the point? For me, none, unless the artist requests and needs that level of detail provided. If I say Clark's in "Downtown Metropolis, daytime, busy, on the sidewalk," then I'll probably get something that's along the lines of what I intended.
On the other hand, if the look of the comic is important to the story (I need a certain character to have a certain facial expression every time he says a certain phrase) then I would want to be specific about that. If something's wrong wiht the world, I'd want to mention that. If I need the tone and image of the comic to look a specific way to benefit the story, then I should go into as much detail as possible to convey that.
But at the end of the day, comics are to tell stories in an interesting and artistic medium. Even the late, genius Will Eisner agreed that art was there to serve the story, not the other way around.
You could do worse than Will Eisner.
(edited to add: Don't be too hard on that random page of comic script up there; I just made it up on the fly as I wrote this post/article/thing. On the off chance that I start writing Superman after Richard Donner quits, I'll probably do a little better of a job.)