I drove for dollars, now what?

[Jonathan Lipson]

Over the weekend I started driving around the area in which I live, and was honestly a but shocked by how many properties I came across that were either vacant or in a major state of disrepair.  Within a fairly concentrated area I found about 15 such properties, took some pictures and recorded the addresses, but I'm not really sure what to do next.  

I know I need to research the properties and track down the current owners, but once I do, what's the next move?  Should the first attempt at contact be a letter, knocking on the door, a phone call?  Maybe a mix?

I'd love any advise that could be offered on how to make contact and, probably more important, what to say.  

Thanks!