Depends on how picky you are. The more we travel by RV the pickier I have become. I do not like noisy places right on freeways. Many if not the majority of well rated parks out of Woodalls or similar book are on busy roads. If this makes a difference to you check out the next few places you are going to be with one of the map systems on a laptop, tablet, or smartphone.
In demand places in the Summer like Yellowstone, Oregon Coast, and other public parks should be booked WELL!!! in advance. WA State parks booked months and months ahead for summer. Same with CA State parks.