We just go and make no reservations however we travel short days and start looking for a place to stay early in the afternoon. We also do not travel on Fri or Sat as those nights can be a problem with the weekenders out. We have been turned down once in the last 5 years but see many turned down later in the day. If you have a given place you want to go you can call in the morning after 10 or so that way any one not being able to make it to that park should have called in so you may be able to fill in for some one that can not make it. Good luck in your travels.