Fwiw, I've become mildly obsessed with this topic, and have written up a couple articles that may help:
* How to talk to customers: http://customerdevlabs.com/2013/11/05/how-i-interview-custom...
* Which customers should you talk to first: http://customerdevlabs.com/2017/03/20/who-are-early-adopters...
* How to ask for conversations: http://customerdevlabs.com/2014/02/18/how-to-send-cold-email...