4. Resolve their action

The player says what their character does. Establish how the situation changes, and/or what their action reveals about the situation.

Did they trigger a player move? If so, which one? Resolve that move. If you aren't sure whether they triggered a move, or you need more info before resolving it, ask questions. Clarify their intent and/or how they're going about it. Discuss with the table.

When a player triggers a move, then follow the move's procedures. Reveal whatever information the move entitles them to. Work with the player to establish how the situation has changed. (See Player Moves, for more detail.)

When a player's move prompts you to add something to the fiction, and you're not sure what to say, then look to your GM moves for inspiration.

If they trigger a move and roll a 6-, then they mark XP and you make a hard GM move (unless the move specifically says otherwise).

If they do something that doesn't trigger a player move, then they're looking to you to see what happens. Did they ignore a threat or trouble that you warned about previously? Make a hard GM move.

Otherwise, say what happens and how that changes the situation. Maybe just say "Okay" and then either shift the spotlight or say "Then what do you do?"