i try to drink as much water as possible after I stop drinking for the night, before I go to bed. Just keeping hydrated.
also, my bio major roommate once recommended eating a piece or two of bread before going to bed because it soaks up the alcohol. i don't know if its total BS or not, but i have never gotten a hangover after doing that.
Drinking lots of water before and after you drink alcohol helps a ton - a lot of the "hangover" is dehydration. I also subscribe to the greasy food theory - a piece of pizza will keep the hangover away!
drink high quality vodka, as high in percentage as possible.
you'll get buzzed easier with drinking less and HQ vodka doesn't tend to cause headaches (i only got a headache once when my friend kept on giving me one Margarita after another and her british BF kept on chugging Tequila into the bowl of Margarita. else i tend to stick to vodka and vodka cocktails.)