When I'm drinking at home, I drink water with my libations. If I'm having hard liquor, I tend towards those that I prefer on the rocks.
I also will make sure I'm properly caffeinated to my own tolerance (which is fairly high)- if you end up with a caffeine headache the next morning, it makes the hangover headache that much worse.
Greasy sausage or burgers late at night after drinking or the following morning, if you can keep them down in the first place, will help quite a bit.
Generally, the only time I still get hangovers is when I'm drinking away from home for very long periods. In January I was partying with friends several hours from home and planning to get a hotel that evening (which I did), and drank fifteen 22oz mugs of Yuengling lager in a 11 hour marathon (plus a couple of shots, I believe)
I'm a big guy, and I've got the lineage for holding my drink, so I never blacked out or lost control. I swayed, but was still coherent enough to know when I needed to go sleep it off at the hotel (and to make those arrangements, since I'm not enough of a selfish moron to drive drunk.)
The next morning however, the water debt caught up, and the massive dehydration had set in. This is why I'd already stashed a liter of Dasani and a 20oz bottle of mountain dew (salts and caffeine), and gave myself an hour to drink both.
Right as rain