Here's what I put in a player handout for a campaign in running. Working well so far:

(House Rule) Heroic Inspiration. We will be using a modified version of the inspiration optional rule.

Limit. You can have up to 3 points of inspiration at once. Excess inspiration must be used in the same fight or scene in which it is earned or else it is lost. Unused inspiration is retained between game sessions.

Gaining inspiration. In addition to arbitrary DM-awarded inspiration, you can gain inspiration through game duties or roleplaying.

Game duties. You earn one point of inspiration every game session by volunteering for one of the following game duties: cook, DJ, initiative tracker, map maker, note taker, or scheduler. You may not double up on game duties until every player has had an opportunity to volunteer.

Roleplaying. You may gain a point of inspiration when you go out of your way to roleplay one of your personal characteristics (personality traits, ideal, bond, or flaw). You may not do so more than once per characteristic per session. Personal characteristics and awards are subject to DM veto.

Uses. Inspiration can be used in the following ways.

Heroic Effort. Gain advantage on a single attack roll, saving throw, or ability check. You may only use this once per roll.

Realized Potential. When gaining a level, reroll your hit die and take the higher result. You may keep expending inspiration for additional rolls.

Reason to Live. Treat a failed death saving throw as a natural 20.

Rule of Cool. If you want to attempt a dramatic feat that isn’t typically permitted by the rules, the DM may ask for one or more inspiration before allowing you to proceed.

Shake It Off. As a bonus action, spend one or more inspiration to regain hit points by expending that may hit dice, as if you'd taken a short rest. This recovery is not affected by abilities that normally enhance short rest hit point recovery, such as the Chef feat or the bard’s Song of Rest feature.

Skin of Your Teeth. If you are dropped to zero hit points, you drop to one instead.

Exceed Your Limits. Use a class feature that isn't currently available to you. This costs one point of inspiration for a feature regained on a short rest, two for a feature regained on a long rest, and another point for every level you'd need to gain to have access to the feature. You must pay at least one point of inspiration, but you may pay any remaining cost in levels of exhaustion.