Beginning-line improvisations are great for helping students learn to establish conflicts on stage. Divide students into groups of two or three.  Give the students a beginning line.  Tell them they must show on stage a conflict that features that line.  Once the conflict is established, i.e. once the audience sees clearly what the dispute is about, they are done.  Give them a short time to talk about what they are going to do, then have each group present its conflict to the class.   A few of my favorite "begin" lines: I can't do it. Never in a million years. All right. I'm not saying another word. I love history.