Okay, this sounds weird, but it works for me, and for about half the people I have told about it. Sit still and wait for a hiccup. Learn to recognize what it feels like when one is about to happen. Next time you feel one coming, concentrate on stopping it. Don't think of anything except stopping that hiccup from "slipping through." Like I said, though it sounds weird, apparently about 50% of people can do it.