So I've never taken a cross-country road trip before, but I'm currently planning a doozy.

In little more than a year I plan to be on the road visiting many national parks, cities and other landmarks. I want to keep my plans loose, since I will be gone for so long, having a just enough structure to be able to plan wisely, with plenty of room for spontaneity.

My question is this:

To those of you who have experience visiting and staying in national parks (specifically the big ones - Grand Canyon, etc.)How far ahead of time would you suggest I book my stay at the national parks that are likely to get booked up?

I will likely book a few of the big guys before I even leave to ensure I have a spot, especially at the ones that are far from other accommodations.

Also: if anyone has any suggestions of good places check out, or ones that book up fast -- that would be much appreciated!