A friend of mine has a company in which people sign up and can get money for referring others to sign up as well. He has a website, and his method of signing up right now is just to send him an email and he figures out all the rest. Anywho, someone recently asked him for his referral link, which he obviously doesn't have. And he asked me for help, and I have no clue :P

How could we go about setting up this kind of referral program? Like, you know when you click a referral link and someone signs up for something, the person gets credit for the referral (like on a forum, or something)? It can't be all that complicated, can it? Basically, I'm thinking you visit the site through the referral link and when you send the email, it automatically says in the email who referred you.

Even if you know of any sites I can look through to get ideas what to do, that would be appreciated as well :) I just have no idea how to set something like this up.