I'll try to give you some suggestions that have worked for me, but chances are they won't work as well on everybody.:

• Thiamin.- Vitamin B1. After you drink your liver starts transforming Ethanol into para - formaldehyde and then it burns it down to CO2 and water. If you drink too much, your liver can't finish what it began and you get intoxicated. It isn't the alcohol that gives you the hangover, it's the by-product. So if you want to help your liver help you then B1 is the number-one choice for an overworked liver. I prefer Roche's Benerva ® 500 mg., but almost any half a gram of B1 will do fine. It's not a bad idea to also take a B complex t give your liver some B6 and B12 to work with.
• Buffer solution.- During heavy drinking (>2 lt.) your gut's pH drops down radically. That is what makes you feel heartburn. A good idea is to take a good buffer solution before you start drinking, before you pass out, and as soon as you come out of coma. I prefer Andrews Salt ® (Sterling Products Intl.);, but if you can't find it in your country, all you need is a mild base and a mild acid, e.g. sodium bicarbonate 2.18g and citric acid 1.84 g with magnesium sulfate 0.88g and sodium carbonate 0.1g. If you have problems with chemistry you can take an Alka Seltzer ®, it would work fine and the aspirin that it contains may even help you with your headache.
• Food.- Not any food but The Right Food. The food will depend on you because it has psychological implications. Seafood is the No. 1 choice. I prefer Encebollado, that's a Yellow Fin Tuna (Thunnus albacares) soup with Yucca. Or Ceviche, that's raw mollusks or fish in lemon (but don't forget the buffer). I prefer black clam (Anadara tuberculosa) or Oysters (Crassostrea sp.). A soup of Pig intestines filled with rice and blood (Caldo de Manguera or hose soup) is a good pick-me-up! too. If you don't like that try whatever you feel like having (see my Hangover Food recipes).
• Rehydratation.- Alcohol has diuretic properties (this is the reason you pee so much when you drink). Usually when you stop drinking your body will be dehydrated. Water is the most frequent choice for rehydratation, but it's not the best one, you also need to replenish some electrolytes lost during the drinking. A good habit is to drink Gatorade®, or any oral rehydratation salt sold in drug stores (like Pedialite®). A more classic approach is tomato juice or V-8®, which are both high in Potassium.
• More Alcohol.- One of the problems of a hangover is that your body gets used to alcohol, so when the levels go down you can bring them up again and forget about the pain. The problem with this method is that sooner or later you must stop drinking, and the hangover will be even worst. This method is recommended for vacations or weekends. The choice of what to drink depends on you but I recommend one of the following: Ice-cold beer, Bloody Mary (it has potassium), Tom Collins, Rum and Pineapple or Screwdriver. Try to avoid drinking the same drink you were drinking the night before.
• Throwing up.-  Puking is a another great way to get better from your hangover. When you throw up, you get rid of a lot of the alcohol you still have in your stomach, and that way it's as if you would have drunk less (some may say it's cheating, but Bah!). Also, you get rid of a lot of stomach acid and anything you may have eaten without noticing that may be rotten or poisonous. I also recommend having a bowel movement, which enables the insides can be cleansed from both ends.