The simplest cure is don't drink in the first place.
Oh yes, and remember that the morning after getting drunk, the chances are high that you are still over the legal limit for driving. Just because you don't feel drunk doesn't mean that your reactions and judgement are those of a sober person.
I'll have to third this. One of the main causes of a hangover is dehydration and electrolyte loss. By doing this before you go to bed, you've given your body a chance to recover and you may even get some real sleep.
Yeah, best one I've found so far is to stay up an extra hour or two, finish a tumbler or so of water/juice/gatorade/(non alcoholic bev), and pop two aspirin before hitting the sack. Doesn't totally wipe out a hangover, but takes it down a notch or three.
If you are really, really drunk praying to the porcelin gods before starting that process can help as well.
Alcohol metabolism varies a lot by individual, some variables are genetics, weight, frequency of alcohol use and medication history. Bottom line, alcohol is eliminated at a steady rate of grams per hour as opposed to most other drugs which have "half-lives"
For an illustration, we can use the old rule of thumb from driver's ed. That recommends allowing 1 hour to metabolize 1 serving of alcohol. Obviously, if a person pounds down 8 doubles in an evening (hey, if we're talking about hangovers, we're most likely not discussing light drinking) it could easily take more than a typical night's sleep to get below the legal limit.
Alka-Seltzer, preferably before you go to bed as well as after. If you throw up the Alka-Seltzer, go back to bed for the day is lost.
Seriously, if Alka-Seltzer made us feel as good when we are sober as it does when we are hungover, it'd be illegal. Get the flavored ones if you need training wheels. I've found the cold medicine variety works as good as the regular, sometimes better because it contains antihistamines.