For four years in high school, I performed group improv. I remember only a little of what I learned.
Aside
Once, in college, I met a woman during a Blood moon. She told me she had a biblical name and wanted me to guess it. Told me it was old testament. I was drawing a blank, but suggested "Uh, the whale that ate Jonah?"
"Yes, my parents named me after the whale that ate Jonah, you got it."
The answer was Miriam, Moses's sister. Anyway, we got to talking while waiting for the moon to do its think. This may have been one of those "blood moon slash super moon superevents that were all over Facebook at the time."
The point is, Miriam did improv at the college, and invited me to practice the following week. I'd told her that I'd done it in high school, and gladly accepted.
That Tuesday, I went looking for the performance and ended up lost in a maze of hallways (it was in the most confusing building on campus, where each flight of stairs rotated 90° so you were always getting turned around).
Anyway, once I got in, we were to write down various phrases on paper, and then go up one at a time, enter a scene, and find an excuse to read our line (blind). I think they did something similar on Who's Line.
When I entered the scene, it was a dinner with a friend. I completely froze, unable to find any way to enter my phrase. What I should have done, I realized immediately afterward was say, "You know, my mother always used to say a prayer before dinner", and then read off whatever random bit of wisdom was written on my card.
I did not do this. I made small talk for much longer than was appropriate, panicked, and read my line with no prompting. You could hear the flub. Everyone in the room did.
I'm not sure if Miriam thought I was lying about the improv thing, but needless to say, I never heard from her again.
The Three Line Scene
One person establishes a scene, another responds, then the first responds again.
In those three lines, you've established who we are, where we are, and what we're doing. Usually this is a conflict, but it could be an introduction (meeting the parents, for example).
Who should be a relationship
Where is specific
What doesn't have to be a lot.
Dialogue
The dialogue does lifting. On a commentary for Firefly, Whedon talks about how the episodes aired out of order, so the second episode acted as the pilot.
Really, he says, your first six episodes are the pilot. You have to assume that each one of them is someone's first.
The second episode of Firefly has Kaylee coming out on a mechanic's dolley covered in grease. Establishing.
Jayne grunts and calls Mal his captain. Characterization, relationships.
Zoe grabs Wash and says something like "I need to talk to my husband". Relationship.
We can see this all done in a rather heavy-handed way. That's OK! That's improv.
You don't have to say "My dear wife, this is a beautiful day at the beach for use to have a picnic" (source), you can say "You're right, dear, the beach was a good place to celebrate our anniversary." It can be a little natural.
But utility is more important.
Tying it to D&D
HexJunkie shows the utility of dialogue with
“Welcome back to the Lion Heads tavern adventurers, I’m the barkeeper Tabatha, stay and enjoy one of my fine brews.”
Perfect, no notes.
In D&D you do have the luxury of being able to use descriptive prose to narrate these details, however framing them in the form of dialogue allows you to engage players directly through speech whilst also filling them in on pertinent details. Ideally, then your players can add to the scene with their own dialogue and decisions rather than glazing over at your long descriptions.
YES! Boxed text is often too much!
Hex goes on to argue that the 3-line scene can establish NPCs with a three-line scene
Sister A: ‘Thanks for meeting me in this forest grove sister, it’s a beautiful day to go for a walk.’
Sister B: ‘Yes it is a beautiful day to go for a walk, and I can’t wait to meet to start worshipping Selune.’
Sister A: ‘Yes I do love the way we worship Selune together and sing to her in this glade.’
Junkie admits this sounds forced on paper, and by the stars does it! I would not use something this forced in one of my games, but the takeaway is good: a short scene where you establish key facts. SHORTER IS BETTER.
Yes And
This is the critical piece of advice most people know about improv. You're always building on other people.
You can do a "no, but", but it's better to let your colleagues contribute.
Aside: my biggest mistake
In high school, I once ruined a scene.
In another performance, I was a mime, and thought it would be fun to translate that to improv. The idea, which I proposed, was that I would start out as a mime, and at the end reveal myself to be a con artist, and not a mime at all!
Good for hijinks, that.
The problem is I left my team out to dry. They only had two people instead of three. When I had ideas, I couldn't contribute them. I couldn't talk. I cut myself out of the scene, and they had to do heavy lifting. We did not do well.
But yeah, if your player's character wants to do something, let them. Make up a thieves' guild, let them stab a scorpion with its own tail for poison damage, why not? The point here is fun and collaboration.
Yes, I know that's contentious. There are some who think that the GM is god, slowly unfurling their masterpiece over their players, who are but mere pawns in their grand story. Blah blah blah.
Make statements, don't ask questiosn
Hexjunkie makes this suggestion, with a story from their own improv failures. It's good advice, though in an RPG scenario, questions can be interesting. Though, as they point out, a compelling statement can provoke questions on its own.