Heard this from a friend and it has worked 100% since then.

Drink from a glass, from the rim opposite from where you normally drink. When done, it looks ridiculous, but it does work.

About a week ago I thought I had an incurable bout of the hiccups. Never really had them before other than maybe for a few minutes. I was at our neighborhood pool, having a few cold beers, and they started up. I was recently prescribed an antihistamine to knock out some poison ivy and I guess the interaction between the meds, the beer and the heat caused them. It was miserable. I was able to control them for a few minutes at a time, but I swear I had the damn things off and on for 10 hours. My chest was sore the next day, like I ran wind sprints. Anyhow, the way I got them to stop was sealing a freezer bag around my mouth and inhaling/exhaling until they were gone. Your respiration will become really heavy as the oxygen depletes from the bag, and you'll obviuosly get dizzy. Once it got to that point I pulled the bag off, and viola they were gone.