I think the best exercise for a playwright is observation. If you get into the habit of observation – specifically looking at people, places, and things, you ‘ll never run out of material to write about. This is a oldie but a goodie exercise because it takes observation to the next level through theatrical application. Observe an individual, create a few character details, write a monologue.
1. Go to a public place. Mall, cafeteria food court, library. A place where you can easily observe others.
2. Pick an individual who is doing a mundane activity. Folding clothes in a store, eating, reading, trying on shoes.
3. Come up with a few character details for this person.
4. Write the inner monologue of this person. What are they really thinking about? Focus on inner thoughts that counter their outer persona. If they are calmly doing something on the outside, focus on an opposing emotion for their inner thoughts.