If you want to maximize performance, eat 3 hours before the ride, then nothing until the ride. Hydrate a bit the day before the ride, but drink normally or even a hair subnormally the day of - you don't want to have to pee on your shoes. If you use coffee, instead of drinking a cup before the ride, take a caffeine pill. On the bike, use foods you have digested easily in prior training and shoot for 250 cal./hr., and a bottle of water/hr. This is most important the first 2 hours, less so the last hour, just the opposite of what you'd think.

Don't eat the food all at once. If you are using Clif Bars, for instance, open one end of the packages and break them into quarters before the ride. Eat 1/4 every 15 minutes. You see TdF riders reaching into their jersey pockets, grabbing a little something very quickly and sticking it into their mouths. Do that. Those little Bento Boxes that velcro to your top tube are great for solid food and gel eaters. No nasty mess in your jersey pockets for your soigneur to clean up.

If your stomach gets weird, stop eating and just sip water until you feel hungry again.

Don't beat the crap out of yourself on the early hills. Save that for the later hills. Plan for one water stop.