Check the Texas Hunting Regulations on their requirements. Most states don't go so far as insisting that you have that permission in writing. However, if permission is required, and someone complains, your hunt is going to be interrupted or ended until the issue is cleared up. Having it in writing is always a good idea.
I made a practice, beginning years ago, of having a County highway map with me in the car, and when I got permission to hunt someone's land, I had them block in the acreage on the map- sometime different parcels, not connected-- and then write on the back of the map their name, their phone number, address, and the date I have been given permission to hunt their land. I always extended the landowner the curtesy of a phone call a day or two before I expected to hunt his ground, telling him what time I might be there, and always checking to make sure no one else was going to be hunting the land when I was there. I didn't want my hunt spoiled, and I didn't want to spoil someone else's hunt. I also asked about gaits, which should be closed, and which should be left open, whether there would be any livestock graising on the ground, and if so, in which field, and I asked if there was anything else I should know before I go out. One time, the farmer complained about someone leaving trash all over his fencerow. He knew it wasn't me, but I told him I would take garbage bags with us and we would pick up the trash, if we could drop it in his burn barrel when we finished the hunt. You have never heard such a change in tone of a man's voice on the phone. We not only cleaned up the trash for him, but knocked on his door after the hunt to give him one of the pheasants we took from a very successful morning hunt. And we put the trash in the burn barrel so he would know where those bags came from, just in case he forget my conversation.
There are lots of ways to thank a landlord for allowing you to hunt his land. The curtesy of a phone call, when he may not remember that he also gave you permission to hunt, asking about the fences, gates, livestock, etc. picking up litter, and sharing your game are all little things you can do, short of paying him cash, to say, " Thank you very much!"
