Hydrate. Drink lots of water, preferably also before you go to bed. After that, fresh air and some food, preferably food that sits solidly in the stomach, such as pasta.
It didn't work so well for me this time before going to bed I normally have a couple of brews (coffee with lots of sugar) and a few slices of toast then I'll try a force a pint of cordial down. That usually sets me up for a reasonably good start when I wake. I'm obviously a little out of practice because I did all that last night and still feel bloody rotten this morning.
But having just had my second coffee and a small glass of fresh orange I'm starting to feel normal again, and the wife is up now so I can feel a bacon butty coming on.
Don't drink so much! Or try switching what you drink. Some drinks just seem better at making a hangover than others. We used to drink a "Bloody Mary" the morning of the hangover and it really seemed to work. The problem is that you feel a bit better so you have another, and another, and another...and you end up drunk again. But it appears to work.
p.s. If you have a hangover from too much wine the night before, if you drink a bunch of water it seems to make you feel drunk yet again. Talk about getting your money's worth!
Know what your drink. Beer has a good water2alcohol ratio. Whine doesn't, so you have to drink water additionaly. Never drink shots or hard alcohol (except you are russian which is ok due to genetics).
To me it must be the last drink I had because before everything was ok
Strong drinks like vodka and whiskey are OK if taken in small amounts, but not to get drunk. Sipping on a good whiskey, just for the taste, is not just OK, it's excellent.
Also, don't drink while sitting. You won't feel how drunk you are until you get up. Occasionally, bite your lip. If it starts to feel a bit numb, stop drinking.