To be sure you have a place, book the site. If check in is at 2 but you plan on showing up at 8 or 9 in the morning, book the night before but let them know you are showing up the following morning. Same thing at the end, book Sunday night and the campground does not care if you pull out Sunday night or Monday morning.
If you are just showing up early, be sure you know the policy, if they do not let you in and you cannot back out of where you pulled in you could site for awhile. I have seen people parked at the entree nice of a place waiting for the exact minute of check in.
