Hiccups are caused by the lungs being out of sync. To stop hiccuping you have to get them to reset the breathing pattern.
This can be done best by slowly breathing in through your nose until you have as much air in your lungs as possible. Then hold you breathe for 3 seconds and slowly let the air back out through your nose.
Repeat Step 1
Your hiccups should now be gone as your lungs have reset. If you have hiccuped before completing step 2 then you will have to start over from step 1.