Hangovers are primarily caused by two things: dehydration and the impurities (congeners) that give different kinds of booze their individuality.
Alcohol is a powerful diuretic, causing your body to lose great quantities of fluid. Not even the water content in beer is sufficient to replenish it, let alone that in mixed drinks. Drinking water along with alcoholic beverages does little to help, because the diuretic effects of the alcohol just move it right on through.
As the alcohol is metabolized by the liver, even more water is consumed. By the time you wake up and are beginning to be halfway sober, you are clinically dehydrated. This can add to the mental confusion caused by the alcohol remaining in your system, the upset stomach, and also contributes to the headache.
The congeners are more easily avoided: skip colored booze (including wine and champagne) in favor of lighter-colored liquors, or beer. The exceptions are gin and tequila, which contain invisible congeners that make them nasty hangover helpers.
On awakening, sip water or Gatorade. Gatorade is better, because it has sugar in it, and your blood sugar is likely to be low. When you think you can keep it down, eat a little something to help with the blood sugar. Then continue to suck down liquids. They will help your liver with the alcohol, if any is left, and will rehydrate your body. Keep drinking water occasionally until you feel “cured.”
You can try all the other remedies, too. Just don’t forget the congeners and the dehydration. They’re the real culprits. Finally, the only 100% cure is time…or sobriety. Ask yourself why you subject your body to all of that. Try to come up with a good answer.
PS: One more hint, not directly related to hangovers, but definitely bearing on your health — if you’re taking medication, all that flushing of liquid can reduce the length of time the meds stay in your body, and seriously affect their therapeutic value. You should not drink much alcohol, if any, when taking medication.