Contacting Prospective Sellers on Foreclosure Deals

[Michael Reid Parrott]

I have a lead on a property that is currently in preforeclosure and I want to attempt to purchase the property subject to the mortgage. However, I am having a hard time getting in contact with seller. Would my best option be to send him a mailer? Are there effective methods out there to obtain people's phone numbers or email addresses? Would simply knocking on his door be a bad idea? 

Let me know what you guys have done in the past. 

Thanks!