Water...
... before going to bed. It works.
Yep, a glass or 2 before bed and no matter how much you drink you'll be fine in the morning.
That's the cure, most of a hangover is really dehydration, rehydrate between drinking and going to be and you'll be fine. Also helpful is to not drink cheap booze, the rest of the hangover is caused by side toxins (besides the alcohol itself) present in the booze and cheaper booze tends to have more toxins. Drink the good stuff and rehydrate (I generally go for about 16 to 20 ounces of water for every adult beverage I had) and no hangover for you.