Hiccups, hiccoughs, call them what you will -- they are not pleasent.
The first option is to try eating several teaspoons of sugar. You will know when you have taken enough as your hiccups will be cured or you will be sick.
The "work every time" method is to completely cut off the sufferer's air supply for a little while. This is done in this way:
Don't warn the sufferer that you are going to cure him, simply approach him from behind and, holding his nose between your thumb and first finger to stop his breathing through his nostrils, cover his mouth with the palm of your hand preventing him breathing altogether.
After a very short while he will begin to struggle. DO NOT let him go until until he appears to be in great distress -- then you may. At this point he will inhale deeply and, no doubt, ask you what you were thinking of. His anger will soon turn to admiration when he realizes his hiccups are cured.