Passenger briefing

Make their flight enjoyable
I don't know if you flew a general aviation plane as passenger before becoming a pilot or not, but beleive me this is not always an enjoyable experience. One factor possibly making passengers feeling bad onboard is their lack of knowledge. This difference between you and them can make their interpretation of things stressing.

Typically, the noise of a landing gear being retracted and hitting the ceiling of the plane can sound really strange to someone hearing it for the first time. And you certainly does not want you passengers being stressed or even worse, panicked, because of that.

A short information from you can make them feeling safe, and their flight will be much more enjoyable.

Important information
Your passenger briefing must be short, make them informed, and if possible not scary. I mention the last point because a good briefing must include some safety information, including but not limited to:

1) Critical phases of flight
2) How to open the doors / evacuate the aircraft
3) Safety belts, and life jackets if applicable.
4) Fire extinguishers

Talking about such topics before the flight can make your passengers feel unsaf, so present these information in a calm environment, not while boarding or taxiing.

About the route
An important point I include in my briefings is a brief description of the route to be flown, and especially the departure procedure. A low level turn after take-off can seem risky to a non-pilot. So if you have to fly such a thing, inform your passengers in advance, so they won't be surprised.

Don't forget that most of time, your passengers are with you for leisure. Let them know that there is no problem to come back at any time if they don't feel good. There is no reason to fly the 2 hours flight you planned if your passenger does not feels well on board, so inform them that you can fly back at any time.

Make the difference
The passenger briefing can play a key role in making the flight enjoyable for the passengers. Missing it can change a stressing event a pleasure. Practice it with fellow pilots if you're not used to it. This will make you a better pilot, even if it has nothing to do with your flying skills.

And if have to cope with a passenger that does not want to get in the plane at the last moment, don't try to force him, he would only get more stressed. Give him as much time as needed to relax, and if the flight is cancelled, don't regret it. It is much better to have a coffee with a stresed person than having to managed a panicked passenger in flight !