Have a friend turn and stare at you and command you to hiccup. This works better if your friend knows to do this without needing you to ask. Tell them to wait until you are not expecting it, if possible.
If you are a teacher and a student is hiccuping, take the student to the front of the room and make them hold a piece of rolled up paper to his or her ear and tell them to take ten deep breaths.
Have someone startle/scare you to the point that you gasp without meaning to do so.
Do something that takes all of your thinking -- like solving a difficult math problem.
Think about what you had for dinner the day before, then the day before that and so on. Don't give up, keep thinking.
Pick out a minute detail on an object about 2 feet from you (a speck of dirt on a coffee table, a letter from a single button on the remote control). You will stare at this very small area while you concentrate on your breathing. Breathe very slowly, yet regular. Don't take huge breaths or anything like that, just breath slow and regular. Do not divert your attention to anything else other than what you are staring at. By doing this, you are taking away your acknowledgment that you have the hiccups. You are putting your attention on something else. After approximately 2 minutes of staring at this object (don't worry, you can blink) and concentrating on your breathing, your hiccups will be gone.