One day, first visit
Arrive at the coast for breakfast. Walk the pier and the beach for an hour. Drive north to the coastal gardens and take the garden loop. Cross inland at midday to the sugar mill ruins. Lunch in the county seat. Spend the afternoon at the agricultural museum and drive the farm road west. Return to the coast for dinner.
Weekend, two nights
Day one: coastal leg end to end, gardens in the morning, beach and pier town in the afternoon, sunset over the Intracoastal.
Day two: plantation ruins and creek trail in the morning, county seat and historical museum at midday, agricultural museum and the western farm country in the afternoon.
Optional third morning: a paddle on the creek or a preserve boardwalk before heading home.
History focused
Sugar mill ruins, county historical museum, the Kings Road alignment on the northern leg, the old cemeteries that hold the founding families of the county, and the railroad geometry of the county seat. Add St. Augustine the following day and you have the whole colonial arc in two days.
Outdoors focused
Creek paddle at dawn, hardwood hammock hike under the ancient oaks, lunch packed, swamp boardwalk in the afternoon, surf fishing off the beach at sunset. Three preserves and a state park fill a long day easily.
With children
Beach and pier in the morning, farm animals at the agricultural museum after lunch, ice cream in the beach town, and a short boardwalk trail before dinner. Keep the driving segments under twenty minutes and the day works.
Rainy day
Museums in the county seat and at the coast, the marine attraction at the north end, and lunch somewhere with a window. The oak canopy roads are at their best in light rain, and traffic disappears.