Last spring I took an Introduction to Improv class with a group of three others. It was a very brief introduction to this comedic form, but I already picked up on its connection to mindfulness and serendipity, and I see why pickup artists like Neil Strauss made the study of improv part of their "training". Improve prepares you to work with what you've got; to be spontaneous; to go with the flow.
The first exercise is a "make a sentence game". Your group stands in a row, and the first person begins a sentence with just one word. The word may be simply the, her, or they, and then each person in the line adds a single word. In this way the group builds a sentence, and then a paragraph, and then a short story. To play this game well, you must not anticipate what the next person will say, because you just don't know. Perhaps a sentence goes like this: "The | dog | looked | sad | when | he | fell | off | the..." If you're the next person in the line, you can say something logical, like "porch" or if you like, "paraglider". The next person has to continue with something that fits, somehow. If you try to predict where the story is going, you'll probably be wrong. It helps you learn to stay in the moment.
Another is called "Yes, and..." It's very simple, and may seem hokey, but it forces you to build positivity in your exchange. Try this next time someone says something you disagree with, or points out something incomplete. Here's an example of the exercise.
Taking improv classes is a great way to build confidence and learn to respond to your environment. It can be especially challenging for introverts, but very worthwhile.