Eat before you're hungry, drink before you're thirsty, little and often is the rule.
It's pretty simple really.
The average body when stoked-up will store enough Glycogen (sugar) energy for about 30 to 40 miles depending on pace, after that you'll might start to bonk. A good bellyfull of slow release food helps go further, but 40 miles/60km is a pretty good yardstick. If you're not planning to go further, then no probs, but if you do you'll need to take on more fuel, and ideally you'd start taking onboard some food before then. If your first energy input is at 40 miles it's too late, remember there is a time lag for digestion, even for gels.
I nibble jelly babies from the off, energy drinks, gels etc are all part of peoples strategies for constant and gentle fuelling from the start.
For bigger miles then a good food stop is important for me, burger and coke, bacon butty, sandwhich does fine, I'm a monster for pork pies! The further you go, the more real food you need.
Simple really, just keep fuelling from the start and you'll go far without problem!
When home, pint of milkshake, 15 mins cold bath and you'll feel amazingly good.