First try walking around for a while. If that doesn't work,
you could try exercising for a while(sit ups, etc.) Eating a large meal might help. If that doesn't work, then you could try drinking a cup or two of licorice root tea, and perhaps also taking 400 mg of magnesium(as magnesium ascorbate or magnesium citrate).
Make sure to get enough fiber in your diet, and to drink enough water.