The ultimate printed guide used to be Woodall's, which is now published as the Good Sam Guide and is available at Camping World. $10 if you are a GS member; $25 otherwise, but worth every penny. It is about the size of a big city phone book and list basic info on thousands of campgrounds. Some is more accurate than others, but it is generally correct.
The "modern" way is to go to {www.rvparkreviews.com} and enter a target city. Keep in mind that only parks that have been reviewed by users are listed and obviously some reviewers have an ax to grind. Throw out the "best" and "worst" reviews and consider the rest of them as average. I like to then go to Google Earth and see what the surrounding landscape looks like.
There are a couple of I-pad aps for locating RV parks.
Have fun out there.
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