Most importantly it will allow you more first times on stand. Most landowners have had experiences with 'slog' hunters and are concerned about safety. If you have a hunter-education card display it when asking permission. Relay the fact that hunting his land is a privilege and you will show respect for his land and livestock. You might offer to give him a hand with some of his summer chores.
Many landowners prefer to deal with one hunter.
If you plan on bringing friends be sure to clear it with the landowner. Leave your telephone number, describe your hunting vehicle, give him your vehicle license number, find out where you can park and ask if there are any times when you shouldn't hunt. Assure him that you will not build any permanent stands and you will remove all your portable stands at the end of the season. You card and a gift is always a good idea. If you harvest an animal, offer to share some with him and his family.