This puts me in mind of the Rules of Improvisation, which I think might be of some use to gamemasters worldwide. Here, now, are the Rules of Improv, which we should all keep close to our hearts:
1. Yes, And: "Yes, and..." is a magical phrase, full of potential and discovery. It acknowledges the offer you have just been given, then builds on it. "Yes, and" is the foundation of improv. It says to your scene partners (or players, as the case may be) "I trust you, and I accept the wrench you just threw at me;" it acknowledges that you and the players are building the world together, and it may give you things to think about.
In the game: "I cast detect arcana on the sword the Prince was using!" "I make a Notice roll" "I knock down the mayor!" may all seem like tiresome phrases; to first acknowledge and then build on these actions may enrich your game. "You detect faint strains of magic on the sword; the wizard knows this may simply mean it's very old and has been used to slay magical beasts in the past" is a great way to handle the first; yes there is magic and it's not a +5 Holy Avenger, but it's got a little history. "You quickly scan the room; there's a fireplace over there, lit, there's a table in the middle, and the orcs are all seated on solid-looking chairs" may lead to more questions about the environment, which leads to more interesting combat. "The mayor picks himself up and lowers the reward" acknowledges that player actions have consequences.
2. Don't play drunk or crazy: Onstage, this is a real problem; in RPGs, this is a little different (since it's fun to play drunk or crazy characters). Let's look at the reasons this rule exists: At the core of this rule is the concept of denial, that is, your scene partner rejecting the reality you've set up. Imagine we're in a scene where we're on the moon; if your scene partner then says you're having a hallucinogenic episode, then we've taken a step back - we're no longer on the moon, we've lost the characters and conflicts we established when we were on the moon. How's this work in roleplaying? Easy: The players only know what you tell them. If you give them unreliable information, expect them to act on it and get mad at you later.
3. Remember the Big Three: In improvisational theatre, you have about sixty seconds to establish the three things you fall back on: Relation, Location, and Motivation, or Who, Where, Why. It's impossible for the PCs to have any sense of purpose without all three of these coexisting.
- Relation: How do the characters know each other? Not just the PCs, but the NPCs: How do they know the player characters? Do the NPCs know each other?
- Location: Simply put, where are we? This is bigger than "Tarth" or "The Ten Towns." Location also informs the rules of the universe - is there magic? Are there feudal kingdoms? Is it the 30s? Are we balloons?
- Motivation: In RPGs, this is split into two umbrellas, "conflict" and "drive." Conflict is supplied by villains first and the party's machinations second; drive is fueled by allies first and the party second. Conflict represents what's at stake - a PC with a childhood foe may find her family in danger and move the party to act; drive represents the rewards and prestige the PCs receive for resolving conflicts.
4. Don't ask questions: Okay, so, I brought this up because it's one of the Rules of Improv. For roleplaying games, ignore it; it's totally cool to ask open-ended questions like "what the hell are you doing" because honestly the players should be answering this. Don't worry about this one.
5. You will look good if you make your partner look good: In improv, it's easy to look good and funny and charming. Hell, at least two of the people in the company got dates from audience members just from being awesome improvisers. The secret is to give your partner your trust, and to give them lots of offers.
Let me break this down a little: Your players take an interest in a the mysterious lake you intended to be a mere piece of scenery; now it's your job to tie this to whatever plot you had in mind. In the end, this makes you look much smarter than you are and gives the players something to talk about - because it turns out everything they did at said lake revealed pieces of the puzzle! In reality, it was just you, panicking, adjusting your adventure notes and encounters to the thing the players were interested in. You made the players look suave and intelligent; in turn, you look like you had everything under control.