I'm not a truckcamper, but mine's a nimble enough setup that I think, camp, and travel like one. I'm also a dyed-in-the-wool boondocker, but do a lot of pre-trip "planning", if you want to call it that.
That involves first locating/checking the rules for whatever Public Lands I'm headed for. If I've never been to the area before, I usually travel to a "familiar" location close by where I can begin my search for the perfect campsite in new territory early the next day.
I'm mostly an Oregon/Washington Boondocker and have done enough of it that I have a store of Old Reliable overnight sites on the way to just about anywhere therein. Funny, though, how sometimes that can turn into a change-of-plans...I made a "quickstop" last year on my way to the Okanogan that turned into a solid week on the Cle Elum River just because the weather and the unexpectedly beautiful spot I stumbled over were too great to give up sooner.
Part of the beauty of the process, I guess...