I eat lots of protein 2 days before. I eat high fiber the day before (I prefer beans). The day of the ride I carb up with massive amounts of oatmeal for breakfast, and carb up during the entire ride.
I ride 50-65 miles in Z2 and Z3 2 days before. Day before I take it easy in Z2 ride for 25-40 miles.
If there are hills around, no worries, just keep it in Zone 2.