2. Selecting the Characters
There would seem to be little need, in this day of wide curiosity about all the forms of writing and those of playwriting in particular, to warn the beginner against straying far afield in search of characters whom he will not understand even when he finds them. Yet this is precisely the fault that makes failures of many otherwise good playlets. The whole art of selecting interesting characters may be summed up in one sentence—choose those that you know. The most interesting characters in the world are rubbing elbows with you every day.
Willard Mack—who developed into a successful legitimate playwright from vaudeville, and is best known, perhaps, for the expansion of his vaudeville act, “Kick in,” into the long play of the same name—has this to say on the subject: “I say to the ambitious playwright, take the types you are familiar with. Why go to the Northwest, to New Orleans in the 40’s, to the court of Louis XIV, for characters? The milkman who comes to your door in the morning, the motorman on the passing street car, the taxi driver, all have their human-interest stories. Anyone of them would make a drama. I never attempt to write anything that has not suggested itself from something in real life. I must know it has existed.” 
 Willard Mack on the “Vaudeville Playlet,” The New York Dramatic Mirror, March 3, 1915.
Precisely as it is impossible to tell anyone how to grasp the dramatic and transplant it into a playlet, is it impossible to show how to seize on character and transplant it to the stage. Only remember that interesting characters are all about you, and you will have little difficulty—if you have, as the French say, the “flare.”
It would seem that a playwright who has his plot all thought out would experience little difficulty in fitting the characters of a playlet into their waiting niches; it is easy, true enough—if his plot is perfectly dovetailed and motivated as to character. By this I mean, that in even a playlet in which plot rides the characters, driving them at its will to attain its end, logic must be used. And it certainly would not be logical to make your characters do anything which such persons would not do in real life. As there must be unity in plot, so must there be unity in character.