What exactly is a link back?
A link back is rather simple. It is a link back to your specific page on the Internet. When the search engines do their crawling and such, the greater the number of link backs to your page means the better chance the search engines have of finding you.
How do you link back?
Visit article directories and submit several free articles. In the byline area and the author area do a link back to a specific article or to your index page of articles. You can also link back to any other thing such as eBooks, blogs, businesses and so forth.
Visit guest books. Make a relevant (not spam) comment about the site and include your URL address for the link back.
Visit blogs on a related topic. Comment intelligently on the blog and leave a link back in your signature.
Remember not to spam because people will become irritated and delete your entries. You can also go to free link pages and other places on the Internet to build your link back network.
Read my article about article directories to learn more about them as a possible way to build literally thousands of link backs in a short time span.