Some of the advice above is good, lots of it is nonsense.
You need to remember that people can only remember three things. So your breifing needs to cover the three things that are crucial- how to get in and out and put the straps on- don't touch the controls- if you see another aircraft, tell me They won't remember anything else.
No one has offered nonsense but rather they have offered their own experience plus what has, for them, been effective. Of course the guest will not remember everything but from a full involvement, whenever possible, they will remember the thoroughness and high level of safety applied to every flight. The involvement of the passenger, when it is safe to do so, will most effectively remove much of the misguided mystery of flying and will build their confidence.