Are you using paid search? Or SEO?
My clients tend to favor one marketing option over the other. Using both can be a great strategy, if you use each one to inform the other.
Here’s a fascinating article, Using Paid Search to Shape HARO’s SEO Strategy – Vocus Blog/ Vocus (the PRWeb people) used paid search to discover keywords:
“As we optimize the HARO website, we now know what people are looking for and which of these terms convert to sign-ups. You can see that ‘free public relations’ converts to sign-up at about 19.5% vs. 11% for the head term ‘publicity’. This data will help us determine if we should target content for ‘publicity’ or ‘free public relations’, based on how difficult it would be to earn a high ranking for these terms organically.”