My pre-race preparation is like MartinH - then on the day, i have the 500ml of PSP sports drink before the race, take a small running bottle of PSP with me. I take sips of PSP every mile or so, miss the first water station, then start to pick up water at the following water stations. With the water i do the following: two gulps of water then the rest over my head, throw away the cup/bottle then burp for the next hundred yards or so.
At the finish i down about a pint of water then slosh around the finish area for a 400m cool down jog.