How to approach owners of delinquent tax properties

[Manuel Mata]

I am new to the real estate investing world. For the past month I have "driven for dollars" one day out of the week and have had some success finding abandoned properties and their owners. My approach with them is simple, I tell them I passed by their house and ask if they are interested in doing something with their house.
I also have come across a list of owners who are behind on their property taxes. My question is, how do you guys approach these owners? Do call them and be straightforward and say you saw that they are behind on property taxes and are they interested in selling? Do I send a mailing before making a phone call? What is the best way to open a conversation with these owners?
Thanks,