Some good ideas here. First. If you are so bad that you pass out, and wake up puking there is little you can do other than try and consume fluids slowly. If I am really hung over, then usually any fluids, or pills consumed, come right back up. But still you have to force yourself to drink fluids, to rehydrate. That being said, if you are truly this hung over, time is the only thing that will make it better.
Second. Avoid getting yourself to that point. It sounds simple but you have to try to equal your alcohol intake with Water intake throughout the drinking day. Hot Weather can make this even worse. Also the amount of food in your stomach is very important as alcohol will absorb into the food. A sure fire way to be hung over is, drink a bunch of hard liquor on an empty stomach and with no water.
Third. If you are drinking vodka, make sure it is a good quality vodka. Stay away from the bottom shelf brands of any hard liquor. Also stay away from mixed drinks with a lot of sugar. If you drink 8 rum and cokes, that is a lot of coke. People don't think twice about consuming mixed drink after mixed drink, but would you ever drink that much soda in a couple hours? For some reason all that sugar with the alcohol and no extra fluids gets you. Some Micro-beers like the heavy hop IPA's, (even good quality ones) if you drink 6 or 7....or 12 have been known to give a wicked hang. Some micros also have a much higher alc %. But it is always the heavy hops that get me.
Fourth. Cheap anything is bad, No Shit, but a real killer is the cheap wines. The worst hangover I have ever had, (and I have had some bad ones, over 35 beers, or over a fifth of liquor) is when I drank a gallon of Carlos Rossi wine one time in college. I was puking and dry heaving for 10 hours the next day. The sulfides and fruit content of some types of cheap wine can be a killer.
Last . I guess your real question was what to do when you already HAVE a hang over. But often by then it is too late. If you plan on an all night bender, take a multi-vitamin the day before, day of. B- Vitamin is the most important. I have heard that if you can stomach coffee it will help with a headache but I have never found it helpful. The best cure would be an I.V.
"beer before liquor never been sicker, liquor before beer, your in the clear." not a bad saying but I have proven it wrong before.