This service focuses on a simple premise: You scratch my back and I'll scratch yours. So, you just build your network of contacts and refer the best you know and hopefully they'll do likewise and everyone benefits from the exchange. Referral Key does all of the dirty work and helps you track every transaction, analyzing everything for you too.
You can advertise your business on Referral Key and get listed by your location and industry. They will also register your listing with many search engines. This all enhances the odds of consumers finding your listing.
Membership to Referral Key isn't free, even though they do let you create an account for free and allow you to receive up to three referrals without incurring any charges. Once you've reached three referrals you'll have to decide on which membership plan you want. There's a Silver Key plan for $10 a month and a Gold Key plan for $20 a month. The differences are detailed on here.