Probably the best way is to take a gift like garden veggies or some fruit of your own labor then ask if there are chores they need done in exchange for riding on their land. Express an interest in maintaining their property so they know you won't trash it. Friendships are reciprocal and not just one way. That said, I would never let a stranger ride on my land under any circumstances because if they get hurt then I am liable. Even if they wouldn't sue me, their insurance company could. So I would have to know that person would lie to protect me which means they would have to have been a friend for many years. The unfortunate reality of the litigious society in which we live is there is no way for landowners to protect themselves other than keeping people out. And there are so many bad apples out there who promise one thing and do something else that from my perspective it isn't worth taking the chance.