One other tip that has been helpful to us: there are NF and private campgrounds outside most of the entrances to the park. We like to drive the park (mostly the Lamar Valley) so, we camped just outside the park at one entrance and then drove back through the park and out another entrance. This kept us from having to double back. Also, the NF (and private) campgrounds outside the park are way less crowded. There are boondocking opportunities outside the park as well. Keep this in mind if you're not able to get a spot inside the campground on a particular night.