Well, I learned about twenty-five years ago that vitamin B-1 and orange juice before you go to bed after drinking moderately more than was wise will usually guarantee a hangoverless morning.If you drink enough to get mild alcohol poisoning, there isn't much that will help. If you drink enough to get severe alcohol poisoning (we all knew it's a poison, didn't we?) You'll be lucky to live long enough to need to worry about the hangover.
I've found that if I mix lots of different drinks, I'm more prone to a hangover. A friend and I downed a liter of vodka and was on our second bottle in less than 30 mins and I wasn't affected at all the next morning. I felt pretty damn good that night too.
Trying this and that for mixed drinks does me in real quick. Gotta pick something and stick with it.