there have been several good suggestions here, one I was recently introduced to was a buisness card. It gives your name, address, and a written promise to be ethical if given permission. It also provides a form for permission to hunt on the other half, one half for the landowner to keep, and one for them to fill out and return if they decide to allow you to hunt thier land. I think it in addition to the letter in the mailbox, with either your phone # or a return addressed and postage paid envelope would be the way to go. This is not particularly in response to the original poster, but just a idea in general

Corey