There’s a lot of good notes in this post by but my favorite part came right at the end, and I think it is relevant to any improv format.
If you are like me, you usually plan your first line when you walk into a scene. Do you do that in real life when you walk into a room? I certainly don’t. In real life I just enter a room and see who is there and start talking about whatever pops into my head. Try doing that in a monoscene. Just come on stage, without an agenda or first line, maybe give yourself a small task like, a reason for coming in, but once you are out there, just respond to whatever is said to you.
And forget about the plot. Don’t plan anything going forward. Try to stay in the moment and surprise yourself with every new beat that happens. If you get an idea of what should happen next, just do it right away, don’t plan it as an ending. Make it happen now when you have the impulse. The story will take care of itself.