You would be surprised how much further you get if you go meet them face to face looking clean cut and presentable. You may be the nicest most honest guy in the world, but if you show up looking scruffy, it sets a bad impression right from the get go. As mentioned above, leave the camo at home. Drive up in a nice vehicle, be overly polite, no foul language, even minor stuff like hell and damn..etc and really emphasize how much you will respect their land and follow any rules they have. Let them know it will be just you, you won't be bringing your buddies and other family members. And if you get refused, still be polite and thank them for their time. I have actually had them change their mind when I was understanding about their reasons for not allowing me to hunt. - "I totally understand, I would feel the same way if other hunters had littered on my property and left gates open..sorry that happened to you"
But also, be prepared for flat out NO! If a piece of land looks good, you probably aren't the first one asking for permission. They may be fed up with people asking, or in some cases they just aren't a very nice person.