A tell-a-friend (TAF) script is like online word-of-mouth advertising. It's a free way to get other people to tell their friends and family about your site. That's why it's important to make your website as useful and unique as possible.
I was floored at the number of people that used my tell-a-friend-script on www.smarttoad.com.
When I launched it I didn't really expect it to get that much activity. To my surprise, I received about 75 to 100 referrals per month.
There are two ways to get a TAF script on your site:
1) Install it on your own server
2) Use a 3rd party
If you do this, you have to have your own domain name or at least a web host that allows you to install scripts. Most free providers do not allow this because of security reasons.
Installing it yourself will require you to know a bit about uploading and configuring files on your web server, but I'm sure your web host can help you.
The CGI Resource Index has a ton of different TAF scripts and many of them are free. Another
benefit of hosting the script yourself is that most of them offer an option to send a customized "thank
you" email to the referrer. This is yet another opportunity to promote your website.
This is the easiest way to setup a TAF function, but the downside to this method is you don't have complete control over the look and feel.
Since you're using a 3rd party site, the person using the script will be taken away from your site to fill out the form. This is somewhat of a risk because the 3rd party site will have the opportunity to advertise to your visitors.
Although if you do not want to bother with script installation, this is the best option to use.
The CGI Resource Index also has a list of remotely hosted TAF programs.
If you decide to use these scripts, make sure you find one that is secure and uses something like CAPTCHA to protect it from spam.
A CAPTCHA scripts forces the user to enter a letter and/or number combination before they submit your TAF form. This prevents spambots from compromising the form and sending out spam through your TAF script.
Lesson #13 : Traffic Optimization - Create a Custom Screensaver