For the first come first serve spots, do you just show up and claim one? Or do you talk to a camp manager first? How early would you suggest getting up there to get a spot?

You can make reservations in advance and they also first come first serve, but they don't start until 2 pm. They have a manager on site. You can always go online to recreation.gov and look up McWilliams campground and find out their policies.

You just show up and claim. There is a little clip above the number with a dry erase board. If there is a reservation it will be on there. If not you just grab the payment envelope and clip the stub to the clip and its all yours!