How do I approach an off market property owner?

[Scott M Marcus]

I found an abandoned house that was a rental property about a year ago (according to the neighbors). It is a brick ranch with tons of potential but needs a MAJOR rehad. I was able to see the inside because the front door is open---it is rough. I looked up the owner and she is in her 70s. I found her phone number and address. What would be the best way to approach her? Should I use mail, phone, or just go to her house? Thanks in advance! Best wishes.