Always ask if they will accept any of the venison if your hunt is successful. Also when talking in person, never wear any hunting clothes. There's no need to advertise what you want by wearing orange or camo. Being clean and polite always seems to work best. If your request is rejected, politely thank them and move on.
It won't hurt if you bring along a young child. That's what my buddy did when has asked permission with his 4 yr old daughter. The owner and his wife said.."How can I say no to that".
Good luck!