In my experience, it’s product-related blogs that tend to do best with Amazon. Most blogs probably have at least some possibilities (for example here on ProBlogger I occasionally link to a book that relates or a computer or electronic tool that I think might be useful to bloggers) but the reality is that this blog will never convert as well on Amazon as my photography site.
Once you've protected your prospecting pool, maximize your affiliate program by working with the best and leaving the rest. As the old 80/20 adage implies, most of your revenue will come from a very small percentage of your affiliates. Because it can be time-consuming to manage a larger affiliate network, consider selecting only a few companies initially, and interview them before signing them on. Affiliates are an extension of your sales force and represent your online brand, so choose partners carefully.