I usually just start by writing or typing out the scene I want to work on in like it's a book, in the present tense, with the basic details of what's going on around the characters and what they're doing. You can put comments or potential ideas in parenthesis if you don't think you'll remember them. I usually proofread and edit anything that needs changing after writing, then I covert it to an interview-like form, which is easier to understand and see where panels will be. When that's done, I decide how to break up the pages by using the '{' and '}' symbols to enclose the different panels, and the '[' and ']' symbols to enclose different pages. Usually, if I decide to break up a character's dialogue into different speech bubbles, I just put the new bubble's words on a different line. While I'm doing this I envision how I want the page and individual panels to look, and break them up accordingly. After this or sometimes simultaneously, I draw a little sketch of the pages to get more of a feel for the layout and see if there are any problems I need fixing. After working around any of those problems, I start on the actual page. (When reading through the format section, you'll see I don't use more than 10 panels on any given page. This is because it will usually look too cluttered if you do, unless you're using a more American comic style.)
Book form:
Zeikery is walking down a street while it's raining at night. He's wearing a long trench coat, with his hands in his pockets. He looks depressed.
A grotesque salamander demon lights on the lamppost beside Zeik. The humans around don't freak out because they can't see it.
Without stopping, Zeik snarls, "If you don't leave I'll kill you." The demon laughs weirdly and moves to the sidewalk in front of Zeik.
"The human boy can see me, he can?" it says. Zeik answers cooly, "You're a lower-class demon by the look of you. A weakling, easy to extinguish."
The demon laughs again and says, "He thinks he can kill me, he does." Zeik reaches inside his trench coat, the demon still laughing, and his hand comes out with a gun.
The demon stops laughing abruptly as Zeik aims it directly to the demon's forehead; Zeik is close enough that the barrel is only an inch away from its head.
"I did warn you," Zeik says simply before pulling the trigger. The demon crumples to the ground, bleeding freely, and Zeik steps over the body nonchalantly, continuing on his way as he replaces his gun within his coat. "I'll make Eli clean it up...he still owes me," he says softly to himself. He reaches a house finally and enters, taking off his drenched coat to hang it on the coat rack. His mother appears, and seeing the irritated look on his face, asks, "Did you find another one?" Zeik nods. "It was another one of those lizards. They probably have a nest in the abandoned warehouse or something." He sits down at the table, head in hand. "This is normal for my life," he thinks -- (box?). "My whole family makes it their job to 'exterminate' the demons who frequent this world to feast on humans. That's why we're called the Hunters."
Interview form:
Zeikery is walking down a street while it's raining at night. He's wearing a long trench coat, with his hands in his pockets. He looks depressed.
A grotesque salamander demon lights on the lamppost beside Zeik. The humans around don't freak out because they can't see it.
Zeik: *without stopping; snarls* If you don't leave I'll kill you.
The demon laughs weirdly and moves to the sidewalk in front of Zeik.
Demon: The human boy can see me, he can?
Zeik: *cooly* You're a lower-class demon by the look of you. A weakling, easy to extinguish.
Demon: *laughs* He thinks he can kill me, he does.
Zeik reaches inside his trench coat, the demon still laughing, and his hand comes out with a gun.
The demon stops laughing abruptly as Zeik aims it directly to the demon's forehead; Zeik is close enough that the barrel is only an inch away from its head.
Zeik: I did warn you. *pulls trigger*
The demon crumples to the ground, bleeding freely, and Zeik steps over the body nonchalantly, continuing on his way as he replaces his gun within his coat.
Zeik: *softly to himself* I'll make Eli clean it up...he still owes me.
He reaches a house finally and enters, taking off his drenched coat to hang it on the coat rack. His mother appears.
Mother: *irritated* Did you find another one?
Zeik: *nods* It was another one of those lizards. They probably have a nest in the abandoned warehouse or something.
*sits at table, head in hand*
(box)This is normal for my life.
My whole family makes it their job to 'exterminate' the demons who frequent this world to feast on humans. That's why we're called the Hunters.
Finished formatting:
[{Zeikery is walking down a street while it's raining at night. He's wearing a long trench coat, with his hands in his pockets.}{ He looks depressed.}
{A grotesque salamander demon lights on the lamppost beside Zeik. The humans around don't freak out because they can't see it. }
{Zeik: *without stopping; snarls* If you don't leave I'll kill you.}
{The demon laughs weirdly}] [{ and moves to the sidewalk in front of Zeik. }
{Demon: The human boy can see me, he can?}
{Zeik: *cooly* You're a lower-class demon by the look of you. A weakling, easy to extinguish.}
{Demon: *laughs* He thinks he can kill me, he does.}
{Zeik reaches inside his trench coat, the demon still laughing, }{and his hand comes out with a gun. }]
[{The demon stops laughing abruptly as Zeik aims it directly to the demon's forehead; Zeik is close enough that the barrel is only an inch away from its head.}
{Zeik: I did warn you.}{ *pulls trigger*}
{The demon crumples to the ground, bleeding freely,}{ and Zeik steps over the body nonchalantly,}{ continuing on his way as he replaces his gun within his coat. }]
[{Zeik: *softly to himself* I'll make Eli clean it up...he still owes me.}
{He reaches a house finally }{and enters,}{ taking off his drenched coat }{to hang it on the coat rack. His mother appears.}]
[{Mother: *irritated* Did you find another one?}
{Zeik: *nods* It was another one of those lizards.
They probably have a nest in the abandoned warehouse or something.}
{*sits at table, head in hand*
(box)This is normal for my life.}
{My whole family makes it their job to 'exterminate' the demons who frequent this world to feast on humans.}
{That's why we're called the Hunters.}]
---
I did this for Tsukiyono-Miyu, who is going to have a digital comic class and needed examples of scripts! :D Hopefully this helps.... 
If you want to read about it, click here: [link]
This is basically what the beginning of Despero Occult (the original series I'm writing) is going to be like. XD; This was actually the first I wrote of it a while ago before I decided to stop and concentrate on my characters for a while.
