Using a ‘Tell-a-friend’ page can be a really effective way to build your list. They are usually best to implement on the page after a prospect signs up for a free offer. After the sign up page, route them to a landing page, commonly called a “Thank You” page, where you can offer them a special bonus if they introduce your offer to 3 friends. Make sure your bonus complements the original free offer .
There are both free and paid tell-a-friend scripts all over the Internet. Here are just two we’ve tried:
Free Tell-a-Friend
http://www.freetellafriend.com/
Tell-a-Friend Wizard
http://www.tell-a-friend-wizard.com/