The conceptual situation or encounter has primacy in the games I run. I describe the scene with no reference to mechanisms of the game what so ever. The players tell me what they want to do.

If the character is a thief and they want to climb a garden wall and what I want the players to do is get on the other side of the garden wall because the wizard who lives in the house keeps a hungry monster in the garden, I don’t roll dice. I just say, “You swiftly climb the wall and sit astride the uppermost course of stone blocks.” If the wizard is reading through a book looking for a particular passage, he finds it given enough time. No dice necessary.

When failure becomes an interesting possibility then, and only then, do I utilize game mechanisms. At that point, the tension between This Might Work/This Might Not Work has been created. There, at that “beat” is where the game mechanisms are most effective in evoking emotion. When a player immediately goes to, “I roll a check.” That tension is mostly defused. When the DM describes the moment, makes the stakes clear and then tells you to roll the D20…That is when you use the mechanism. That is drama.