Our Paid Search guy has been with the company for years, and sort of does his own thing, so honestly most of my new clients come from referrals of people we are already doing paid search for. We’ve shown we provide value, and then point out that SEO is an option as well.
Then I normally meet with them a few times- first with a basic overview of our costs, then with a deeper dive of where they stand currently (with areas they can fix). The key is to set proper expectations- I always make the comparison of “paid search is like getting money through the stock market, and SEO is like putting money into a mutual fund, the growth happens, but it’s not overnight, it’s slow but steady”