He recommends several outside texts such as The Act of Creation which is a great read in of itself. Make sure that the script has everything that is important to you so that the artist can include it.
If you look at the way professional artists work, they would come up with several prototype models or rough drafts before they can finally hit the right spot and come up with a design that best fits the personality that you gave the character. This also serves as your precursor to making your dialogue and planning what each of the scenes will look like in drawing.
The large letters emphasis the severity of the act. I know that sounds sinister, but the trick is to get the artist to like it.
It can also serve as a warning sign that you may have over-written the page if there are too many lettering elements 15 or less is a good benchmark. The cards can be moved around and reorganized as much as you want.
As a practice exercise, writing your own descriptions of the characters and scenes you see in a published comic book will help too.