There are many ways you can conduct an impromptu speaking session. Here are a few ideas:
The easiest type of question are those you would normally hear in a conversational setting. If you have never seen or tried impromptu speaking, consider questions like:
Asking questions that are obviously not meant to be taken serious is a fun way to practice thinking on your feet.
Speaking about unfamiliar content cranks up the question a notch. Still, don’t expect the speaker to stick to the topic.
Give each speaker three words they must incorporate into their speech, e.g.:
fire brigade, elephant, scissors
When you start the session, ask the audience to write single words on tiny pieces of paper. Collect the pieces and have each speaker draw three.
Advantage: Requires very little preparation
Divide the audience in three groups: “persons”, “colors” and “objects”. Ask each group for a person, color and object. These are the three words the speaker needs to build their speech upon.
Advantage: Requires even less preparation
Pick questions to a common theme, for instance:
Bring a magazine. Pick one article (preferably with a big picture) for each speaker. Give them the headline right before they start to speak and ask them to tell what is in the article. (without reading it).
Prepare 5-7 presentations with 6-7 slides each. Use slides with one big image and no text. Configure the presentation program to switch slides automatically every 20 seconds.
When you run the session, give the speaker the title of the presentation and nothing else. They will figure out a way to comment on the slides on the fly.
Obviously, preparing 30-50 slides is a lot of work. If you know a link to slides with an open license, please let me know.
Story Cubes are a nice gadget that helps you to generate cues randomly. The speaker rolls a couple of dice (3 or more) and tries to assemble them to a story. The dice are available in a physical version and as an app.
Because the dice are quite small, Story Cubes are a better fit for smaller groups.
This impromptu exercise is for two or more persons. Set a topic. One person expresses an idea, the next contradicts and so on.
Start a story. Participants take turns in adding 1-2 sentences.