To clarify this question further I'd say it's more in the meanings of the words.
'On' basically means to be on something to put simply "above" or "amongst". It also gives ownership to something in a sense (the house is ON fire, the painting ON the wall).
It also implies continuation (to go on and on)
Whereas 'in' means more "to be inside" so you're IN a group, or IN control. It can also desribe what you are using to get a message across ("I wrote it IN ink").
Trouble COULD arise when you read that someone is 'on' a jury or council, and yet they are IN an organisation. In this case 'in' is more to be within something and 'on' is more to be a part of something.
Also if you have basic English knowledge your ear may be able to pick up which sounds more appropriate!
Hope I helped! Ty for the question!