I’ve mentioned it a few times in various topics, but I use the Force dice to determine “luck” in my games. When a situation calls for a chancy roll, and the characters’ skills are not applicable because it is luck of the draw, I prefer to use the Force die. It’s flexible, thematic, and has been quite useful for me.
I usually break it down thusly:
Double-light: Something positively good happens.
Light: Something bad doesn’t happen, or something marginally beneficial happens.
Dark: Usually neutral, unless I need to shift the luck towards bad.
Double-dark: Not only does nothing good happen, but something positively bad happens instead.
Sometimes, the situation would call for something bad to be more likely to happen, in which case I shift single dark to be the unlucky counterpart of a single light, and either shift single light to be neutral, or simply remove a “neutral” option, depending on the circumstance.