Decide on the story. Good pantomime has a comic flavor combined with the fantasy genre, so your story should soar above everyday life. One direction to take is to base your story on a traditional fairy tale. The mythical content appeals to all ages and the basic plot is already established and familiar to the audience.
Define the characters. When choosing your characters, consider the following:
There is always a dame. Dames are popular with the audience and are sure to win a large applause and laughter with every entrance. It is advisory to go for the classic 'bloke in a dress'.
There is always also a villain in any good pantomime. A well-played villain is essential and central to the script, and should elicit a reaction from the audience. The villain is generally considered the star of the show.
The principal boy is loved by the audience for being really good and moral. His character is a very basic, straightforward character and shouldn't present much of challenge when writing your script.
The princess/heroine of the pantomime goes hand in hand with the principal boy. Portray her as a fun, innocent and slightly thick central character.
Stick to a clear structure. Divide the story and performance into two halves possessing two crises. The first half should end with resolution of first crisis and perhaps early signs of second crisis. The second half should be shorter and more dramatic than the first. The second to last scene is usually a community song, while the final scene traditionally contains a large event that has all actors present for the finale.