Know-How Exchange : Advertising/PR

Rob, I have a little sales experience, so maybe I can help a little.
First, I'm wondering what they're thinking when you tell them who you are. Did they agree to have someone call them, or did they know that by checking that box that someone would call them? In other words, is this a call they requested or expected, or not? What I do know, of course, is that everybody wants pictures of their baby. So you know you have that working for you.
Let's say, worst case scenario, it's a cold call. In my experience, most people will decide by the time you've said 5, 10, or maybe 15 words whether they want to hang up asap or not. It's a very short window. Your challenge is to get them to want to hear more, and quickly. A quick stab from me would be like, "Hi, on the sign up form for some magazine you expressed an interest in having professional photos of your new baby. I am a photographer and I am very experienced in baby photos. If you'd like, I could come to your home and make pictures. Then, if nothing else, you can have your favorite one as a free gift." And maybe as a closer, "Do you think you might be interested?" or, "If you'd like, we could look at a night next week."
I've found that asking directly if they want to hear more causes an awkwardness when you request that they respond. Instead you could just pause briefly after the initial spiel to give them a chance to say no thanks.
To really get it a good pitch, you'll have dive in and work it out as you go. Write yourself a little script (I've done this and it helped), and improve it after every call. You'll find what works best for your purpose and audience.
And as you're working out your pitch, remember, hook 'em quick. Then they'll listen.