First line exercise.

Challenge students to write a short stage direction in parentheses, and a single line of dialogue.

In rapid succession, let volunteers act out three of these. Discuss how the first lines gave the actors and the audience some clues about character, objective, mood, and setting -- all in one line.

Now, let the best pair(s) improvise the dialogue to follow the first line. When it veers from credibility or good taste, say, "Cut!" and discuss standards and better possible ways to develop the scene, and have them do "Take Two."

Let whole class pair up to try this exercise. Let some (or all) perform for class, and use second takes to focus on believable development of conflict.