Apocalypse World gives you as a GM a set of Guidelines and Principles to put into every decision you take as a GM:
• Barf forth apocalyptica.
• Address yourself to the characters, not the players.
• Make your move, but misdirect.
• Make your move, but never speak its name.
• Look through crosshairs.
• Name everyone, make everyone human.
• Ask provocative questions and build on the answers.
• Respond with fuckery and intermittent rewards.
• Be a fan of the players’ characters.
• think offscreen too.
• Sometimes, disclaim decision-making.
Could we put something like this together for Mouse Guard?