The right way is to first conduct deep research on a prospect organization, arrive at some sort of possible 'white space' opportunity and then 'ask' the prospect's permission to discuss the findings.
The wrong way is to spam the prospect. One of our clients, who leads communications for a global brand, says she is literally being deluged by spam pitches from myriad public relations firms. They're arriving in ever-increasing numbers, are 'inside out' in their approach (i.e. “We're a great agency and you'd be smart to hire us.”) and are actually counter-productive since they damage the firm's image and reputation.
I have the great fortune to serve on several boards populated by some of the best and brightest corporate communications chiefs in the world. I would never, ever allow my firm to blindly spam these individuals. To do so would violate a business relationship and, even more importantly to me, a personal friendship. That said, I've been able to win new business with some of my board peers but only after a long period of building mutual trust.
So, here's a heads-up to all the new business people at all the PR firms in the world. Stop spamming prospects. Step back and be more thoughtful in your approach and suggest solutions instead of pitching your incredible capabilities. My client will tell you those unsolicited mailers are going straight in her trash can, as is any chance of being considered for future assignments.