It is almost a requirement anymore today to reserve online. TN state parks is online only even though one can do a driveup and take a chance. Payment is required at time of reservation and one can cacel a week prior with a full refund less the infamous fee.
I am a member of Coast to Coast and their reservations are online only. I have never had a problem with a res or been denied a spot. Granted, some very popular parks might be full if you are a guest but I have never experienced that myself as yet.
When we are on the road we call the park directly. For an overnight we start looking while on the road at about 2pm on RVPARKY and call the park and give an estimated time of arrival and I never make a reservation. If we decide to stay longer at that park I go the next morning as soon as the office opens and ask if it is possible to extend for x many days, pay for the extra days and go back to the trailer and relax.
Flexibility is key. I have never had an issue anywhere I have gone, but then I don't go to extremely popular tourist destinations in the high season either, I have that luxury of having my own time and schedule.
