Decide on your terms of use for your play. Ask yourself whether you will allow your play to be performed by amateur theater companies or if you want to prevent others from using your play completely.
Keep your disclaimer brief and to the point. To indicate that you wish to maintain all rights to your play, write a short disclaimer like this: "All rights are strictly reserved." To avoid any breach of use, expand on this disclaimer to reinforce your stance on copyright; state that any unauthorized copying or public performance will not be permitted.
Include in your disclaimer your terms of fair use. State if you will permit your play to be copied and used for educational purposes or if you will grant performance rights to amateur theater companies. Write words to this effect: "Educational use is permitted."
Provide information within your disclaimer of how others can gain permission to use your play for performance and if a license needs to be obtained. Include your contact information.
Give a declaration about your play as a work of fiction, if your play is based on a true event. Write a short statement to say that, even though your work is based on true events, your characters and places used are fictitious and not based on real people and any similarities are just coincidental.