Someone else had posted this tip a while ago. I tried tightening my stomach muscles during the ride and it worked great. The only time I felt discomfort was in the few seconds I let my muscles relax so I could take a breath. I felt a little weird for a couple of hour after the ride, but at least I was not nauseous.
TIP:
"Mission Space: The ride experience varies depending on which seat you're in. The Navigator has the mildest ride, Pilot next, Commander a tad tougher and the Engineer's seat gets the most pull.
Another thing that helps enormously is taking a deep breath and bearing down on your stomach muscles like you are going to the bathroom. I know it sounds crazy but some of the queasiness that you get is from your stomach and internal organs pressing up against your diaphragm. I found myself doing that reflexively on the ride, a function of my own flight training in response to G forces. It also helps to brace your feet against the bulkhead in front of you rather than place your feet directly under your seat. I would recommend going in the morning and eat only a light breakfast if at all at least 2 hours before you ride. Afterward expect to be a little weak kneed for a few moments"