Your brain counteracts alcohol's sedative effects by becoming more excited. Whatever you do, don't make yourself throw up. He recommends Pepto-Bismol if you're feeling nauseated. Avoid taking other pain relievers, such as aspirin or ibuprofen, that will irritate the stomach lining even more, or at the very least, make sure they're buffered. Most hangovers are pretty much done in a day, but be alert to the possibility of life-threatening complications.
Many people fall and injure themselves after drinking too much.
Blows to the head in particular can be very dangerous and may lead to internal bleeding in the brain. Persistent stomach pain or uncontrolled vomiting is another sign that you need emergency care. A quiet New Year's Eve at home is starting to sound better and better.