I am lucky to be able to both write and draw reasonably well, think Da Vinci on cocaine, so when I am exploring the forums and I see talented artists leaving links to their comic scripts the thought of their stories being misunderstood worries me.
Here's what I would consider a useful guide/template for a comic script.
Series: Adventure Story
Written By: Leonardi Cocaine Da Vinci
Page 1
Panel 1 (This should be where you put all the details you want for the panel, some artists need a lot of description and others need very little. Remember that collaborating with an artist is a constant negotiation). James Hero is about 29, he has green hair and is wearing sunglasses which look vaguely like Oakleys, he is dressed in clothes appropriate for the beach but he is not at the beach. (Now we've described the character the artist has a good starting of point and their mind will begin flooding with potential images). James Hero is at the north pole. I want this to be a landscaped wide shot, show a lot of the region, snowy and mountainous. (Notice how I am giving descriptors while still leaving room for the artist to exercise some creative license.)
Panel 2 Pull in close to James, he has a gun in one hand, maybe a revolver in some garish colour to show how egotistical he is (here I am giving direct insight into the character because the artist is not like the reader and therefore you don't have to worry about spoiling the story because you are building the story with them).
Panel 3 Similar to Panel 2. James is looking down at something off-panel. He has his free hand raised to his mouth and is talking to a device on his wrist.
James <-- (This is a dialogue tag which shows who is talking)
Ma'm, it looks like I've found Agent Monday...
Page 2
Panel 1 Big reveal time. This panel should take up the whole page. We look over the shoulder of James to see Agent Monday, a 60 something covert spy dressing in garish arctic gear. He looks something like Peter Falk. Sprawled on the floor in a bloodied mess. There's a ski-mobile just beyond Agent Monday with bullet holes.
James (cont'd)
...killed in cold blood is the best way to describe him.
END OF EXAMPLE
Notice how throughout the example I tried to give references and descriptors for what I visually wanted to see without being completely rigid or overly specific. Again, some writers want their panels to look a specific way and that is fine as long as you're working with an artist who is comfortable with that. Remember also to respect the instincts of the artist, sometimes they'll have a suggestions for a panel layout or character design which might be a crucial improvement to your comic but ultimately (unless they are a co-creator) it is your comic. You are the writer. Good luck.
Artists, feel free to practice with the script example but please credit me as the writer (either "Mythos" or "Tayo Rafferty".