^^^This. (It applies for any bike, and the poster indicates as much.)
I'll quintuple the motion on hydration and food and add some thoughts having just completed my first century ride a couple of weekends ago.
1. Know the route you are planning (or if already laid out) on taking. Intimately. There is nothing like taking a wrong turn and getting lost, then running
low on food or water. It can be demoralizing.
2. Unless you are working towards a PR (sub 5 etc), stop and smell the roses, take pics and use these moments to let your a$$ return to it's original
form.
3. Bring at least 2 spare tubes, you never know when a pothole will take out both at the same time (thank you city of Escondido). Also consider a small
emergency repair kit with a quick connect link. A guy I know did and it really helped another rider who broke a chain going up Palomar.
4. Consider riding with others, whether it be 1 or 2 or a good sized group. Nothing beats fatigue like a companion.