Take a breath as deep as you can then try to pull more air in and hold it for as long as you can.

I heard this a long time ago and know that it works: open your mouth, tilt your head back, and let your tongue relax so that you're breathing through your mouth and not your nose. Hold this position for about 15 seconds or so (breathing through the mouth) - when you straighten up your hiccups will be gone. It's based on the fact that there are no documented cases of someone having hiccups while sitting in a dentist's chair. The first time I tried this, I did it as a practical joke. I drove a party bus (van) around the local college campus giving rides to students between the campus and a downtown bar that contracted to the company I worked for, then brought them back when they were too drunk to walk. It was a slow night and a girl got on with her boyfriend - he had the hiccups BAD. She said that he'd had them all day and couldn't get rid of them. I suggested the protocol I described here - I thought I'd get a laugh at seeing him fall for it. But to everyone's surprise, it worked! She was so grateful, I think I coulda maybe got laid that night if I asked - he was dead to the world, so it was for sure he wouldn't mind...LOL. After that, I got a job that took me on the road and quite a few times I'd run into convenience store clerks with the hiccups. Everyone I suggested it to tried it and it worked - without fail. I use it on myself whenever I get the hiccups - but wouldn't you know it...because I know how to get rid of them, I don't get the hiccups that often.