Take some vitamin B12 before you go to bed/pass out. Alcohol depletes B12 and that causes some of the hangover symptoms. Just don't freak out the next morning when you..ahem..relieve yourself and it's the color of Mountain Dew. It's a side effect of the B12.
Also, a glass of water or club soda with several dashes of angostura bitters. Helps settle your stomach, and there is some alcohol content in the bitters. A little 'hair of the dog', if you will.