Is there a way to make reservations or is it only first come first serve??

You can only reserve the group camp sites but they are usually reserved a year in advance. The rest are first come first serve. 12pm is when you're supposed to be packed up if you are not staying another night, so I'd say, show up around 1230 to get the pick of sites.

It's first come first served, but campground keepers are super nice and will point to you if there are any ppl leaving, but I do believe that you can make reservation for bigger groups though