For daytime flights, bring sunglasses, even on cloudy or hazy days. We can easily climb into really bright sunshine.
For daytime flights, consider bringing a camera. We fly much lower than airliners, so the scenery is much more interesting. If desired, we can circle over points of interest.
You will probably be provided with a noise-reducing headset. This greatly increases your comfort --- planes can be pretty noisy without headsets. An intercom system allows you to communicate with the other people on board. You will be able to hear air traffic control (ATC) talking with us and with other planes. When ATC calls us, the message will begin with our aircraft call sign. Make sure you know our call sign, and if you hear anything even resembling it, stop talking so the pilot can pay attention.
Motion sickness is very rare --- the plane is not bumpier than a car on a typical New Jersey road except in unusually turbulent weather. Even really bumpy weather is no problem if you are used to it --- the fear of bumps is worse than the bumps. On the other hand, if you know you get sick easily, let the pilot know before the flight. Anti-motion-sickness drugs like Dramamine and Bonine are only effective if taken an hour or so before the trip. TransDermScop patches are very nice but are available only by prescription, which requires a certain amount of planning ahead. Also, if you feel yourself getting even slightly queasy during the flight, let the pilot know immediately. Airsickness bags are available. Also, usually we are not more than a few minutes from an airport --- we can land 'till you get over it. We don't mind.
On the other hand, landing a plane is quite a bit more bother than pulling a car to the side of the road, so attend to your restroom needs etc. before flight. Remember caffeine is a notorious diuretic.
If you have a cold or hay fever or any possibility of sinus congestion, let the pilot know before flight. Altitude changes cause pressure changes which can be very painful if you have a blocked sinus. And once again, if you feel sinus pain coming on during flight, let the pilot know, so we can plan an extra-gradual descent.
Do not go SCUBA diving during the 24 hours before the flight.
Please be aware that the all-time number one air-safety procedure is called ``staying on the ground''. Flights can be cancelled or diverted for many, many reasons, including weather, equipment problems, pilot fatigue, etcetera. If you think you have to arrive or return by a particular time, please make backup arrangements.
You are encouraged to look out the windows. If you see another airplane nearby, make sure the pilot knows about it.
No smoking in or near the aircraft.
You can't easily see a spinning propeller, so don't go anywhere near an airplane when the engines are on. Don't fool with propellers, even when stopped, because it is (under some conditions) possible to get the engine to fire by rotating the prop by hand. Better yet, just stay away from propellers.
You must wear your seatbelt during takeoff and landing. Please wear it at all other times unless there is a good reason to be moving around. If a shoulder harness is available, please wear it too.
Front-seat passengers (including licensed copilots) should refrain from ``helping'' with the controls or fiddling with the radios, unless explicit arrangements have been made with the pilot-in-command. Such arrangements are common; just make sure you know who's responsible for what, at all times. In any case whenever you (accidentally or otherwise) flip a switch or bump a knob, make sure the pilot-in-command knows about it.
Please turn off your cell phone before takeoff, and leave it off. It won't hurt the airplane, but it won't be usable as a phone and it messes up the cellular network (because it moves too fast and has a line-of-sight to too many base stations).