Have one or two aspirins *before* you go to bed. That will diminish your hangover the next day.
Also, try not doing what I did : taking the aspirin, and two minutes later there they went in the toilet - and of course, I didn't take some more after that
(oh, by the way, I had drank only 4 beers that night, and was not able to go to work the following day. Call me a wimp)