Often we read articles geared towards e-commerce sites and adjust the
advice as applicable. This recent article [written November 20, 2012] offers
advice specifically for affiliates. This is excellent general advice:
Instead, focus on raising your visibility wherever you can get converting traffic, and focus on making sure that when someone clicks through from the SERPs, you can keep there until they convert.
Source: Link Building for Affiliates - Search Engine Watch (#SEW)
This article gives tips on research, creating unique content, choosing keywords for the Long-tail, using social media plus more and then what might really be helpful is the section on what NOT to do. Check out the article, it was written for affiliates:
Link Building for Affiliates - Search Engine Watch (#SEW)