In an informal survey of some of my fellow freelancers I can tell you that the biggest issue most writers take with cold calls is the idea that they're pestering the person on the other end of the line. First off, let's dispel that myth straight away. Anyone in the business world is more than used to getting calls from various businesses and organizations trying to get them to use the goods or services they have to offer. When you truly think of yourself as a business with a valuable service to offer, it becomes nothing more than a run-of-the-mill business call. No pestering whatsoever!
Another problem is fear; fear of rejection, fear of making someone "angry", fear of someone leaping through the phone and strangling them to death. I can assure you, the last example certainly won't happen (although it's a killing move I've never seen before in a horror movie; maybe I should write that down!) The second is highly unlikely to occur unless you've truly caught someone on the absolute worst day of their life, in which case it's not about you anyway. As for the first, yes, there is a chance that the person on the other end of the line might say no. If that happens, be gracious. Send them an email afterward thanking them for their time and reiterating the services you offered over the telephone; this will leave a positive impression on them and you might be surprised when you get a call from them in the future requesting your services.
And another tip that I've heard; don't think of them as "cold" calls. Warm them up by mentioning a friend in common or a LinkedIn connection. Tell them you follow their business on Twitter or Facebook. Just be friendly, be yourself and be confident that you have something they need. You might just be surprised as you watch your client roster grow.