FYI - I have 'earned' the right to fish quite a bit of private land by providing the owner with a pre-printed card that list my name, address, phone number, vehicle description and license number, a list of Oregon fishing & hunting clubs that I am a member of.
And I offer to clean up the areas or even do some light work in exchange for the right to fish/hunt the property. I also look like a outdoorsman and not a convict or transient. I drive up to their property when they are present, am polite, and do what I say I am going to do.
This has earned me the right to fish multiple private Oregon ponds, streams and rivers. Some will ask for payment to use the property or park there, but most, after the initial shock of my asking have given me permission without hesitation. Since I have been doing this, I have actually made some new friends, as well as some fishing buddies, as some join me for some fishing and to ask about the various organizations that I belong to.
And remember it is their property.... don't act upset if they say, "no"... just thank them for their time... some may surprise you by reversing their first decision.
p.s. I get to fish a lot of private properties in Washington, Yamhill and Columbia Counties like this.