You can do affiliate marketing in two ways, one, by working with affiliate networks, and two, working with affiliate programs. A lot of companies and websites offer offers affiliate program, you can see their affiliate program by checking the bottom page of the website. Tracing affiliate sales can be a daunting task, therefore, those who cannot offer their own affiliate programs affiliate company. For instance, they team with companies like Clickbank, Linkshare, CJ Affiliate, etc.