Consistency and Fairness
Source GM Core pg. 15
As an arbiter of the rules and the person who's setting the scene for the action, it's in your best interest to appear fair at all times. Your main defense against appearing unfair is consistency in your rulings.
Achieving consistency is as easy as explaining why you're ruling a certain way and comparing this ruling to past rulings you've made in a way that makes sense to your players. For example, you might say something like “When Dae swung from the streetlamp and attacked the skreeling, I required an Athletics check as part of the action and gave a +1 circumstance bonus to the attack roll. Hanging from the catwalk to attack the garaggakal sounds similar, so why don't you roll an Athletics check.” Do this any time it's applicable when you make a ruling, but don't feel compelled to do so for truly new rulings.
Through the course of playing, your previous rulings will form a set of shared preferences and an understanding between you and your group—or even become formalized house rules. Over time, your players will think about these examples when planning their actions, which can improve consistency during play.
Achieving consistency is as easy as explaining why you're ruling a certain way and comparing this ruling to past rulings you've made in a way that makes sense to your players. For example, you might say something like “When Dae swung from the streetlamp and attacked the skreeling, I required an Athletics check as part of the action and gave a +1 circumstance bonus to the attack roll. Hanging from the catwalk to attack the garaggakal sounds similar, so why don't you roll an Athletics check.” Do this any time it's applicable when you make a ruling, but don't feel compelled to do so for truly new rulings.
Through the course of playing, your previous rulings will form a set of shared preferences and an understanding between you and your group—or even become formalized house rules. Over time, your players will think about these examples when planning their actions, which can improve consistency during play.