Best way to acquire adjacent property to develop into multifamily

[Mark Gliebe]

So here is my scenario.  I own an investment property in Louisville, KY and I am looking to acquire adjacent parcels (specifically 2) in order to develop and build 50-70 units.  I have made contact with adjacent property owners, but have given them verbal offers and both them did not even counter with a price. Through our conversations I know they are both willing to sell so its not a matter of if, but when.  What is the right negotiating tactic?  How do other seasoned commercial investors approach off market owners who have not seriously flirted with selling until you approached them?  Thank you and look forward to hearing everyone's advice.