Elizabeth Spiers has some good tips on how NOT to pitch:

Inexperienced entrepreneurs often present investors with non-disclosure agreements (NDA) before sending over an executive summary or a pitch for their multi-billion dollar double secret plan to sell books over the Internet. Those go directly into the circular file. Why? Because the investors and analysts look at similar deals every day and for every entrepreneur who thinks he or she has an idea no one has ever thought of before, there are usually 7 or 8 entrepreneurs who have. The entrepreneurs, of course, never believe this. No one could have possibly come up with their ultra-niche, ultra-obscure business idea. They only thought of it while scuba diving off the coast of Iceland on LSD, and it's therefore cognitively and circumstantially impossible that anyone could replicate the thought process that led them to stack this widget on top of that widget in such an unconventional patent-pending way. But the reality is, investors get stacked widgets and déjà vu all the time. They don't sign NDAs because they're not going to expose themselves legally to accusations that they stole an entrepreneur's idea and gave it to another entrepreneur (as if anyone would go to the trouble.) And an entrepreneur who presents an NDA is regarded as naïve and unacceptably unfamiliar with the standard fundraising process—thus immediate rejection and, in some cases, gratuitous lectures and profanity.

In media, this is a dealbreaker that occurs while the pitch is in pitch purgatory (the editor has read it, but hasn't assigned or rejected) or after an initial rejection. But it's important because it essentially guarantees that an editor will never, ever look at a pitch from the freelancer under any circumstances. Here's the scenario: Multiple freelancers and maybe a staff writer or two pitch the same story. The story gets assigned to one of them or was assigned separately by another editor or perhaps, was already assigned but hasn't run. The story appears and the pitcher's immediate reaction is to call the editor and complain that the story has been stolen from them. Editors have almost no incentive to steal a story under the worst of conditions and no incentive whatsoever under the best. I think editors stealing stories happens at about the same rate that people get struck by lightning. It's risky and unnecessary. As a result, nothing is more infuriating than to be wrongly accused of stealing a story and having to defend yourself as an editor—especially if the story in question is completely unoriginal and has been pitched multiple times.

The freelancer, of course, has no way of knowing what has been pitched, what hasn't, or when and how stories are being assigned internally. And the natural corollary is that the freelancer has no actual evidence that supposedly stolen stories are, in fact, stolen. Accusations are backed only by the freelancer's suspicions and resulting similarities between the published story and whatever the freelancer had in mind, which is never self-evident proof of plagiarism. In the rare instances where stories are stolen and hard evidence is available, it's worth prosecuting, but if all you have is a suspicion and two topically similar stories, keep in mind that any spurious accusations will permanently destroy your relationship with that editor and likely, that publication (and if the editor feels particular insulted at having his or her professional integrity questioned, all of the editor's editor friends and their respective publications as well.) Make the claim when necessary, but don't do it lightly.