How I got a 100% conversion rate cold calling prospects for customer development

Coincidence: Steve Blank just appeared on Hacker News with some article about contacting busy people. He said something similar: offer something in return. In that case it was your expertise in your market, in return for strategizing advice. Here its blog exposure for a guided tour.

I suspect this theme could be expanded upon. Anybody else got a story of creating genuine rapport by offering something first?