In addition to all the tips above, I have one to add.
I have never been so drunk as to get sick, so this goes for those who don't go to that extreme:
Besides drinking a good 1-2 pints of good old water before going to bed, I also pop a multivitamin with the water. I've found that the water takes the majority of the edge off, but the addition of the vitamin seems to eliminate it.
I remember reading that alcohol (or it's digestion) somehow removes certain B-series vitamins from the body, and that lack can lead to a bad morning. Not as bad as the dehydration part of a hangover, but it contributes.
At the very least, DRINK WATER. If you're coherent enough, perhaps a vitamin may help?
-Germ - not a health scientist by any stretch.