Another possibility is to wake your child up before the time that the terrors usually start, to disturb the sleep cycle and hence prevent the night terrors. (easybabylife.com)
It's made to help them get to sleep and stay asleep as well as also preventing night terrors. (mummymiller.com)
There's no definitive way to prevent night terrors because no one knows exactly what causes them. (babycenter.com)