Apart from rallies or special events, we have bought campgrounds maybe a dozen times in the last ten years. So, we use planning software and set up to spend the night at:
Cabela's - often have a free dump
Casinos with 10$ electric (first come first served so slim chance)
Cracker Barrel - but often the big spots are filled with 4 wheels
Walmarts - good time to reprovision too
Casinos - too many rules and sometimes you get stuck next to a reefer
Any known free (or real cheap) flat spot
Highway rest areas - often noisy
Truck stops - usually make rest stops look good
But then we are travelers, not campers.
Matt