Inspiration

I've decided to experiment with using Inspiration in our current Lost Mines of Phandelver 5th edition D&D campaign. To that end, here is how I'm going to apply it in the actual game.

Using Inspiration gives you Advantage on an attack roll, saving throw, or skill check. (When you have Advantage, you roll two d20s instead of one, and keep the higher number. Likewise, Disadvantage means rolling two d20s and keeping the lower one.)

First of all, everybody will start each game with exactly one Inspiration. You can only have one Inspiration at a time, so it behooves you to use it. But you can only use it during certain times.

Taking an Inspired Action

You can use your Inspiration when you're doing something that ties into your character's personal characteristics (ideals, personality trait, bonds, flaws).

1. You can use it to give yourself Advantage.

As an example, let's suppose you have the Personality Trait, "My greataxe is a family heirloom, and it’s by far my most precious possession," and during a battle it gets knocked away, teetering on the edge of the cliff. If you put yourself in danger to try and save it, you could use Inspiration.

2. You can also use it to give Advantage to SOMEONE ELSE with their own actions.

Suppose that your Personality Trait is "I see people as marks for a con and have difficulty feeling true empathy for them," and you decide to help a fellow conman size up a potential victim. You could use your Inspiration to give them Advantage on their attempt to trick their target.

3. Lastly, you can use it to give Disadvantage to SOMEONE ELSE.

For example, if your ideal is "I must protect my friends," and you decide to help take the brunt of an assault, you could use your Inspiration to help them fend off the attack and give the enemy Disadvantage on their attack roll.

The important part is it has to connect directly to your personal characteristics somehow, and that you're actually in a position to be able to do something. You can't just toss in an Inspiration to help someone if you're not even in the same room, or help defend them from someone if you're not actually able to do so, etc.

Earning Inspiration

Once you've burned up your Inspiration, you can earn a new Inspiration point by volunteering to impose Disadvantage on your roll based on one of your personal characteristics, OR by making a decision that creates a significant setback. Either one has to be related to personal characteristics.

1. Imposing Disadvantage based on a personal characteristic

Suppose you have a Flaw, "I'm easily tempted by shiny objects," and you're asked to roll Perception in a room studded with glittering gems and treasure when you're searching for a trap. You could volunteer to impose Disadvantage on the roll because your character is too distracted by the gems to notice the obvious traps laying about.

2. Making a decision that creates a significant setback

You can also earn Inspiration back when making a decision that creates a setback. Suppose you've taken an oath to never lie, and an enemy asks you an incriminating question. You answer honestly, giving him critical information or a significant advantage.

Character Development

People change and grow over time. As your character experiences challenge and loss, triumph and adversity, they might believe in new ideals or shed previous ones. Sometimes the DM will invite you to wipe out an old characteristic and replace it with a new one that reflects the current character. For instance, if you had an Ideal, "The Church is always right," and your character goes through a harrowing experience that could cause him to lose faith, you might strike out that Ideal and replace it with something new.

This is still a work in progress, but it should give you an idea of how it works.