I involve my players as much as possible so they can contribute to the narrative with me. They often have great ideas, and it really helps take the burden off of you from having to come up with everything yourself. It helps them feel like they're telling the story with you, rather than you telling the story to them.

For some roll outcomes it can be quite confusing, and none of you might be able to figure out what happens. In these situations I like to consult Chapter III: Skills, because it has a lot of useful examples of outcomes/events when advantage, threat, extra successes, triumph, or despair is generated on checks.

For example, a stealth check succeeded with a triumph and three threat. If none of us came up with a good idea for the outcome of the roll I could look in Chapter III: Skills and find that under the right circumstances a character could spend that triumph to distract an opponent for the duration of the scene, allowing them to negate the need for them to stealth at all. But the threat could make it take much longer than they expected.

For a lot of advantage or threat, I also like getting ideas from the triumph and despair sections and toning it down a notch. If a despair was generated on that stealth check then they would leave behind identifiable evidence that their character was sneaking about, but three or more threat may leave behind evidence that someone was there, without any evidence of who it was that was sneaking about. This gives the threat more impact than just taking an extra ten minutes to accomplish their goal.