Require a cashback website. This is an affiliate cashback website like [url removed, login to view] - the idea is that users register to use the service. Once registered a unique i.d. relating to their account is dynamically added to all the affiliate URLs in the site. So, if they make a purchase this can be tracked at the affiliate merchant website i.e. at [url removed, login to view] etc. The site should include CMS for adding merchants, categories etc, email system both html and text for keeping in touch with users, and a referral system whereby users gain money for recommending friends that go on to register.