If you're drinking tonight, you know what you need to do to avoid a hangover. So why don't you ever do it?
Eat before you start drinking. Don't worry about calories. You'd rather gain an ounce or two than make an utter fool of yourself. Besides, maybe it will keep you from being so ravenous when you drink.
Drink water. Drink a bottle of water so that you're not thirsty when you start drinking. It's easy to down a couple of cocktails if you're thirst, especially if you're trying to socialize with strangers, or are anxious about your date. Bad idea.
Alternate each alcoholic beverage with a glass of water or soda. It will halve your alcoholic intake for the night, and keep you from getting dehydrated, which is the main cause of hangovers.
Limit yourself to one ounce of alcohol an hour. Your body can clear that much. Drink more and the products of alcohol metabolism (especially acetaldehyde) can accumulate, leading to a hangover.
Drink clear alcohols (vodka or gin) rather than colored liquors. And don't mix--stick to what you start with.
Consider prophylactic analgesia (taking a pain killer before you need it). The problem is that non-steroidal anti-inflammatories can irritate your stomach, which will be irritated by the alcohol as well. Acetaminophen, though touted as safe, is dangerous for the liver, especially in high doses, and mixed with alcohol.
Do something other than drink. Play charades. Dance. Arm wrestle. Play Scrabble. Make love. Preferably with someone you know. It's time away from alcohol, and it will focus your attention.
There are a lot of ideas about what can be done to preven hangovers. If any of them worked, we'd all know about it by now. But hope springs eternal.
Look here for other ideas.
Meanwhile, have fun, be safe.
Happy New Year!
[Image from Drowned in Sound]