I'm having fun remembering how impossible it was for me to get ready for that first summer in Yellowstone without ever having seen the place. Hell, I didn't even know where it was at first; like a surprisingly large number of Californians, I had it confused with Yosemite. I finally bought a "Story Behind the Scenery" book about Yellowstone. It was a good book--no problem there--but it gave me the impression that Yellowstone is pretty much all geysers. The place is over two million acres, and the geysers are a little tiny fraction of that. So in a sense, there is no way to plan.
Except to know that Yellowstone is the one with the hot water, and Yosemite is the one with the cliffs. And John Muir with his beard and his suspenders, all poetic and Scottish. Also Yosemite is in, you know, freakin' CALIFORNIA, not Wyoming.