Here is my take polishing the dialogue. In one regard, dialogue is far less important than story, character, engaging visuals, etc. Comics is a visual medium and I've always found that rather than kill yourself slaving over word choice in the initial writing stages, its better to throw in some filler "Lock and Load" caliber lines and push through your story. That is, as long as you know you're going to go back and shine it up.
I spent a lot of time doing my homework this past winter, and wrote a blog post a while back that contains pretty much everything I've learned about writing good dialogue. Check it out for some ideas.
But I'll share with you guys an example of polishing dialogue. I first wrote my graphic novel "Over" as a screenplay. I then proceed to write three more complete drafts of it in screenplay form. Each time, every scene got a dialogue polish. And it got another polish when turned to a graphic novel.
Here's a part of a scene from the first draft:
INT. TONY'S OFFICE
Tony sits behind a large, messy desk, littered with comics, bills, empty snack wrappers and Red Bulls.
Have a seat.
You got my email?
And you read it?
You're killing me, Tony. What'd you
think of "Over"?
Tony waves his hands, trying to slow Felix down.
Before we get into that, I have to
ask. Is the "Pendragon" twelve script
finished? Say yes.
I'm here to talk about Over, Tony.
You don't have it. Okay. Fine. I
see you brought the originals like
Got 'em right here.
Can I see them please?
Felix hands Tony the massive folder of art.
Know that I do this because I
respect you and your career.
Tony throws the folder and all the art into the trash. Felix recoils in horror.
You didn't like it?!
Now, here's what actually made it on the page after all those polishes:
(Over updates M,W,F at www.overcomic.com)
Note, the main thing I did with the polish of this scene was eliminate. I got rid of all the chit chat and got right to the meat of the scene. In most cases, I think dialogue improves by elimination, so on a first polish of your dialogue, go line by line and see what you can get rid of and not loose the important beat of the scene.