I have found some good for my needs and wants stops by taking the distance of my destination. Like just a week ago, going from the top of MN to the mid Gulf coast of Texas, about 1,560 miles. I do secondary roads, best i can, clicking avoid highways, no toll roads on the gps and phone mapping.
Dividing the trip into 4 days and 3 nights stops, got me hear. So around 350-400+, miles a day one fuel stop at mid point and just before camping for the night.
Taking google maps on the computer, i find about 200 miles in the trip and look for fuel best/easy to get in and out, most places now have pics of it. About 200 miles gives me a safety net for fuel, if its a heavy headwind. Then another about 200 miles to a chosen campground, with a fuel stop just before and or as close as i can to said campground, to leave in the morning full of fuel ready to go.
Going to an area on the map and putting in search for campgrounds/camping as well as just zooming in closer to see what pops up on the map for camping.
I have found some really simple, safe, nice small town campgrounds, some self checking and pay, not very often, but some free up to X amount of days but usually there is a donation box i donate to. I just look for plugging in, not hooking anything else up, i use my camper for everything, except if a good place to eat out is near, ill walk there.
I have tried the truck stop and walmart thing, and its not my thing.
My destinations are usually monthly or seasonal, so i tend to go back to the same summer place but go to an area on the map for the winter area, and find campgrounds look at the pics, look for reviews and hope for the best. If not, just move to another place after finding one.