Every character begins each session with Inspiration, which is a thing you either have or you don’t.

If you have Inspiration, you can spend it at any time to take an Inspired Action provided that action somehow ties into one of your character’s personal characteristics. If your Ideal is “I will do anything to save a person in danger,” and you want to swing across a ravine on a vine to rescue someone who is about fall into the ravine and hanging by one hand, that fits. You can claim an Inspired Action.

When you take an Inspired Action, you can either gain advantage on an ability check, attack roll, or saving throw OR you can give advantage to someone else’s ability check, attack roll, or saving throw provided you are in a position to assist them directly in some way OR impose disadvantage on someone else’s ability check, attack roll, or saving throw provided you are in a position to hinder their action directly in some way. Whatever it is, the Inspired Action MUST somehow connect to one of your Personal Characteristics.

So, let’s take that “I will take any risk to save a person in danger.” You could do the aforementioned “swinging across the ravine to catch them from falling” thing. Or if they have to attempt a saving throw to avoid a collapsing ceiling, you could throw yourself at them to save them, giving them advantage on the saving throw. Or if a monster is about to attack someone standing near you, you can interpose yourself and give the monster disadvantage on the attack roll. See? Easy.

When you don’t have Inspiration, you can Claim a Setback to gain Inspiration. To Claim a Setback you must either impose disadvantage on one of your own ability checks, saving throws, or attack rolls based on one of your Personal Characteristics OR make a decision that creates a significant story setback, obstacle, or hindrance. When you want to Claim a Setback, simply ask the GM. For example: “I’m easily distracted by shiny objects, so I’m distracted by the giant pile of treasure. Can I Claim a Setback and take disadvantage on my saving throw against the dragon’s fire breath?” Or: “This guy wants to help us, but I distrust all strangers. I’m going to be rude and accusatory of him. Can I Claim a Setback for that?” And then the GM might have the stranger refuse to help or get offended or start a fight. Whatever.

After you Claim a Setback, you get Inspiration. You can use the Inspiration to take an Inspired Action. And on and on it goes.