To follow along with
@chaochou --- in Story Now play as a GM, it's generally best to only define something as "true" within the fiction as late as possible.
It's totally okay to have ideas in your head of what
could be true. Ideas, rumors, possibilities, fronts, NPC goals, etc.
But it's usually best to put forth what
actually is true as a response to play. There will almost always be a twist or turn that results from player inputs or action resolution that will enhance or supplement an earlier idea, or twist the original idea, in a way that makes the idea more directly impactful to the fiction and character concerns.
In this same regard,
be true to what the fiction demands and implies. If and when the most obvious conclusion of a turn of play is in front of you, take it, especially if it adds dynamism and interest to PC concerns. If you want to throw a twist out there, try a technique from Ironsworn and use an "oracle table" or randomizer to choose between possible conclusions.
Be very, very careful about directly injecting your own ideas of "This sounds fun to me" without consulting the other GM principles first ---- Does it follow from established fiction? Does it address PC concerns? Is it the most impactful version of the outcome? Does a recent PC action success or failure require it to help or hurt more than usual? Have you followed the correct procedure as identified by player and GM side "moves"?
*Edit --- one of things I had to learn for Story Now GM-ing is to scale back the level of specificity of my ideas. As a "trad" GM, we get used to defining highly detailed, highly granular notes about everything. Story Now play seems to work better if you take general ideas / themes / concepts, but then let the direction of play fill in the specifics along the way.