Try leaving a note like this on his ladder stand:
Hey stranger! I' m so glad to see someone else will be out here hunting with me. I hunt every day of the season and it gets awfull lonely seeing as the only one I have to talk to when I' m hunting is my black lab. Anyway, I look forward to meeting you and having lengthy conversations while we hunt!
P.S. Now that I know I' ll have company I' ll bring along a couple extra summer sausage sandwiches and an extra 6 pack of Rolling Rock!