A number of years ago I came home from hunting to find a message from local law enforcement on my home answering machine. An officer wanted me to give him a call because my truck had been reported as being parked on a farmer's property without permission. And because that farmer had recently been the victim of some vandalism, he was suspicious.
Of course, it was all a misunderstanding because I'd received permission from that very farmer to hunt on his land about a month ago. He'd forgotten the truck description I'd given him and it only took a single phone call to straighten everything out. However, the episode was a great catalyst to start me thinking of a better way to communicate with landowners via my truck.
I was raised on a farm and thus have a little insight into rural life. I know that every rancher or farmer knows all the trucks in the area and who drives them. If a landowner sees a familiar vehicle, he's comfortable in knowing who they are and what they're doing. But when a landowner sees a strange vehicle in the area, there are two questions he wants answered: "Whose truck is that?" and "What's the driver doing out here?"
Knowing the questions led to some research and eventually I found an answer. I call it a truck tag, and while it's certainly not original to me, I think it's still a great idea. This is just my version and I'll share it with you in hopes that something similar might work for you as well.
A truck tag is simply a piece of paper on which is printed whatever information you want to share with people who see your truck parked somewhere "unusual" and are curious enough to come over and check it out. I target mine at the landowner, and on the tag I print what I'm doing, that I have permission, my cell phone number and my name. I print them at home on heavy paper and laminate them. I leave the top edge stuffed between the side-window glass and the weather stripping whenever I leave the truck.
I keep a handful of different variations in the truck, covering every species of game I hunt and wildlife photography as well. I usually make them about 3 1/2 inches (square) and with an open space at the top so the writing doesn't get lost behind weather stripping. They're cheap to make, easy to use and help with landowner relations. The way I have mine set up might not work perfectly in your situation, so make whatever modifications are necessary and feel free to use the idea.

Use a truck tag to improve communication, relationships with landowners.