are you riding by yourself or with a group? If you aren't going to be riding through any places where you could buy something make sure you bring more food/water than you think you will need. I went through one bottle of endurox, 5 gu's and a mountain dew code red on my first century. If I did one again, I would a little more often. Probably every 30-35 minutes instead of 45 minutes.
Replacing electrolytes is important also on a ride this long especially if you are doing all the work yourself. After the ride, you will probably crave something, go eat it.
Also... don't push too hard too early. The first 40 miles of my ride I felt like I was barely putting in any effort at ~18 mph, but your legs will start to feel it after a while. Miles 65-85 seemed to be the toughest for me, yours may vary.
Days leading up the ride, cut the volume a bit. Don't overthink it, just relax!
drink lots of sports drinks (like gatorade or other) and water in the days leading up to the century.
Eat a good carb meal the night before.
This will help make sure you have max fluid and energy stores at the start of the ride.
During the ride you need a steady source of calories. gels and bars can be good for this, so can fresh fruit, fig newtons and other easy to carry food. I think some where along the lines of a couple of hundred calories intake per hour, but I am not sure on that number.
Make sure if you use gels to drink plenty of water with them.
If you don't have specific medical problems, it's doubtful you need to do "anything special" in the days before the ride. The typical response to questions like this -- is to simply eat "normal food" in normal amounts.
New century riders are no more successful than old hands when trying something "new" for a ride. Just remember to snack while you ride and continue to "sip" water or sports-drinks throughout the ride.