One of the things we will do to a student pilot who experiences air sickness is to make them take the controls. The act of having to fly the aircraft sometimes helps combat the symptoms.
Overall though, it is a mismatch between your vestibular system and your visual system*; your "balance" says one thing and your eyes say something else; the mismatch causes a problem with many people leading to "motion sickness".
(* That's why with seasickness you shouldn't go below decks and lie down. Your eyes say everything is normal but your balance says you are rocking)
Really? Since most of a ship's motion is in pitch, when I feel bad on a ship I go to the lowest accessible deck and walk fore and aft until I find the ship's center of mass. Then I hang out there until I feel better.
Even when our cabin is near the front of the ship so that the pitching motions are maximum, I've never felt particularly bad lying down with my eyes closed. It's walking that'll do it to you.
One drawback to the expensive cabins (other than the cost) is that they're usually on the top decks well above the ship's center of mass, meaning that they move more than the lower decks.
In aviation, as Obviousman pointed out, giving control to the student can help. Also, having the victim of motion sickness look out at the horizon can help - I think ether act realigns how their vestibular system perceives the world (I've been lucky, in all of the instructing I do, none of my students, even when sitting passively while I set up unusual flight attitudes, has ever gotten sick).
As for ships, I think it depends on the nature of the motion. One thing I'noticed, for example, is that in the dining rooms of Royal Carribean/Celibrity cruise ships is that the chandeliers are fixed to the ceiling (does one say "te overhead" when discussing a passenger ship?). This obviously prevents them from swaying as the ship rocks, which might have unpleasant effects for some diners and their companions.
One amusing incident a few years ago was when we were on a cruise with a group of friends. The seas were a bit choppy the first evening out, and the ship's stabilizers couldn't damp it all out. We were sitting at dinner and I noticed that the window shades were drawn, giving us views of fine art prints rather than panoramic views of the ocean. As mentioned, the chandeliers were fixed to the ceiling. Over dessert, one of our friends, a very nice lady, said "Wow, am I glad the water smoothed out - I hate it when it's rough. Ever since I was kid boating with my family on Lake Michigan, it just made me seasick."
I said, "Didn't you notice they're not filling the coffee cups to the top?"
"So?"
"And take a careful look at the water in your glass. See, it's still fairly rough out there. You just can't tell."
"Ohhhhh....."
Y'know, it's the the only time my wife's ever really chewed me out while on a cruise....
