http://gamedame.wordpress.com/2007/10/01/how-to-prevent-motion-sickness-from-halo-3/ at the Army have known about this problem for a long time because of their experience with aircraft and combat simulators.
They have even developed a set of guidelines for prevention or minimization of the effect. Since it’s a very long,
technical PDF document, I thought I would highlight the results for you.
GENERAL STRATEGIES
Adaptation: The only reliable way to beat simulator sickness is to play often and build up your resistance.
Play short sessions at first.
Play only one session per day at first.
Don’t go for more than a week between sessions when you’re in the adaptation phase because you’ll “unadapt” yourself.
BEFORE YOU PLAY
Don’t play if you’re extremely tired or if you have a cold/flu
Turn off all other lights in the room.
Sit far away from the TV ? as far back as you can while still being able to read small text. Try to make the field of view around
the TV set as large as possible to give your eyes some “grounding” room.
WHILE YOU PLAY
Short sessions! Short sessions! Short sessions! I know this is frustrating when you have a cool new game, but try to stop playing
BEFORE you get sick. Play for only 10 minutes at a time if you can. As you get adapted, your game time will last longer.
Minimize your head movements.
Close your eyes when you press pause and turn your head away from the screen before opening them.
If you can help it, don’t do too many “fancy” maneuvers like airplane rolls or spinning around excessively until you get adapted.