I do the B-vitamin thing before going to bed and it always works for me. My regemin is 1/4 tablet each of a B-6 and B-12 supplement. Why 1/4 tablet? Each full tablet is something like 2000% of your recommended DV, so I figure I'm still giving my system a good jump start to replace all I've lost. If I forget before going to bed and wake up feeling like scrambled-@$$, I take one then and about 1.5-2 hrs later can really feel a noticable difference.
I also do a less-scientific method on occasion: the red eye. Raw egg (very fresh), and equal parts tomato juice (or V8) and beer. That gives you a little of everything - vitamins in the V8, protein in the egg, something that feels good and solid in the stomach, and the old hair o'the dog (beer). That solid feeling in my stomach usually makes me feel much better. It's a little thick, but if you drink it fast, you'll hardly notice. Also, don't forget to swallow the yoke in a single big gulp.
I've heard that a shot of olive oil is supposed to be part of a hangover regemin - don't know if it's preventative or reactive. I'd be willing to give it a shot if anyone can attest to it's effectiveness.
Focus