When I used to drink mixed drinks, I always drank those with a citrus base. I also drank a big glass of water and took several Vitamin C pills and two aspirin before going to bed (not Tylenol – it puts more stress on your liver, which is already stressed by the alcohol).
Now my solution is not to drink. It works better than anything else I have tried and it makes watching the drinkers so much more amusing.
BTW, Midol won’t help the dehydration – it contains a mild diuretic, so it will only make it worse.