I take Bonine (2 pills) at bedtime starting 2 days before the trip (helps with the flight too, if there is turbulence) and take it daily for the whole trip. I still avoid "spinny" rides like teacups (spinning is my kryptonite) but I can handle coasters, ride simulators, and the more intense dark rides like TSMM as long as I take the pills. Bonine is less drowsy (than Dhramamine) anyway but taking it at night lets me sleep off what little sleepiness I do get.
I find it helps to space rides out too, no doing intense rides back-to-back, but wait times usually force this anyway, even with FP.
Also keeping a pleasantly full (but not stuffed) stomach helps me, counter intuitive I know but whatever works, right?
If all else fails and I feel it coming on during a ride (rare if I take the pills), I close my eyes for the rest of the ride, that will keep it from getting worse.