DS2 (9yo) gets the hiccups all the time. If he laughs for more than 10 seconds, he gets the hiccups. Sometimes he'll just get the hiccups for no reason. He used to get very frustrated because often it would take a while for them to go away -- the usual tricks of drinking water and holding his breath were useless.
Both boys had their well visits with the pediatrician last week, and the only issue that I had on my list to ask about was DS2's hiccups. Surprisingly, the doctor had some practical information and advice.
Information: frequent hiccup sufferers like DS2 are often shallow breathers. Hiccups are spasms of the diaphragm, the thin sheet of muscle below your lungs that we use to fill them with air. If your breathing is shallow, your diaphragm isn't getting a good workout, and it's much more likely to spasm.
Advice (the cure): Fill your lungs. This is the important part: being careful not to let any air escape, draw even more air in, so your lungs feel over-full. This has the effect of pushing down on your diaphragm. Hold for a moment, then release the air slowly. Repeat the process for best results.
DS2 reports great success with this technique. Not all hiccups are caused by shallow breathing, but it certainly won't hurt to try this technique next time you get them.