You might be a beginner or a seasoned writer (in other fields), the first question that you have to answer when you decide to write a comic book script, before putting pen to paper or firing your computer, is how are you going to format your script?
Before you can really tackle that question, you have to understand the nature of the beast. Scripts, for film, TV, theater or comics, are weird pieces of writing, in the sense that your readers will be very few, from a handful to maybe only one. When you write a novel, a journalistic or academic piece or a blog post, you are most likely aiming at reaching the largest possible readership and many factors play a role: subject, style, grammar, etc… Whereas when writing a script the only thing that matters is whether the artist is able to apprehend your story and vision. He’s your reader, nobody else will read your words except for the dialogue and no one will care if your descriptions were written with flair or style.
So the only factor that matters regarding format, is that the finished script is fine tuned to give the artist all the information he/she needs to transform the script into a comic book. Depending on the workflow dictated by the artist’s personal capabilities and style, you might have to go into excruciating detail regarding framing, composition, color, etc… or you might only need to present things in a very simple and general way for the artist to grasp and develop them from then on. It’s really a case by case scenario and the only requirement is that once you find a formatting style that suits you both, that you don’t deviate from it going forward, so that the artist knows what to expect whenever you send a new script.
A good starting point might be using a tried and true formatting method like film standard format, which will be easily implemented using any of the free or paid software apps available (check out the blog post on Scrivener). You can then adapt the format to your common needs, knowing that the software takes care of the details, letting you concentrate on what matters, the writing.