Think back to your childhood and the colorful characters you knew. Carry a notebook with you at all times. You will be surprised how many characters can be written after a day of simply people watching, and a little eavesdropping. You may even live with some pretty hysterical characters, so start paying attention.
Purchase playwriting software, so that you can be sure your play is in the proper format. Nothing is more irritating than reading an ill-formatted play and being confused about when a character is speaking or where the stage direction is. The software will format the play for you, so that you can focus on the writing.
Write what you know. It may be the oldest adage, and as a writer, you may have heard this advice a million times, but in the case or playwriting, it’s good advice. The character “Madea” in Tyler Perry’s successful plays would not have been nearly as funny if Mr. Perry had not based her on someone he knew. Truth is always funnier than anything contrived.
Make your play character driven. The differences between writing for the screen and writing for the stage are many, but one big difference is in the story’s action. You are much more limited visually on the stage, especially since some audience members may have bad seats. Therefore it is imperative in comedy to make the humor character based and dialogue driven. Audience members may not be able to see a pratfall from the back row, but if the microphones are working he’ll hear your character’s sarcastic wit.
Find your story. Your plot can be dramatic if you desire, because the comedy comes from the characters, even if they are in a serious situation. The strongest plots include a setup, or introduction of your main characters, one central character who has some sort of conflict, the process of solving the conflict and a resolution to the story.
Focus on story. When writing a character driven comedy, it is can become easy to focus on the jokes or funny situations, and forget to move your plot forward. Once your script is complete, take out any scenes that do not serve the purpose of the story. This can be a painful process, as you will be forced to remove some very funny bits, but if the bits solely exist for the humor, and have nothing to do with your story, the jokes would probably fall flat anyway, as these scenes would seem out of place to the audience.