Read through your script and list the characters in order of appearance. Characters are listed in their appearance order in most cases but sometimes productions choose to list the stars first, followed by supporting characters. By listing characters in order of appearance, it helps the costuming and props department plan its work. Characters listed earlier appear earlier in the sketch so their props and costumes should be readied first.
Add the character names to the top of the script page after the title of your script and then the heading "CHARACTERS." Write each character name in all capital letters.
Put a hyphen after each character name and add the names of the actors. Capitalize the actor's name normally and write it with upper and lowercase letters. one cast listing might look like this: "HUCKLEBERRY FINN - John Smith."