If possible, before we book an extended stay at a campground, we do a drive through first. We've found several that got great reviews but during our drive through, we determined they just weren't our style. Going to check out three in the hill country of Texas this fall when we are down there.
If I can't do a drive through first, I'll check on line photos and google earth before booking. If the place doesn't have at least gravel pads for my trailer, I won't stay there.
When I'm just staying overnight, if the sites are reasonably level and it has good electricity, I'm not too picky. If the bathhouses are dirty, I'll use my trailer.