In very simple words, the link popularity of your site means the amount of links coming to you from another sites.

Every major search engine heavily weighs the link popularity of sites when ranking sites. Some engines even claims they won't index sites that don't have at least one link pointing to them from another site.

Why they are doing that ? Just because zero popularity means that nobody has an interest related to your site content. Since nobody is interested, why search engines should consider it ? From their point of view zero popularity is a time wasting.

Under the above circumstances, the link popularity of your site becomes very important to you, especially if you aim to earn traffic by indexing your site in search engines directories.

Let's see what you can do in order to increase the link popularity of your site. First of all you should concentrate on finding sites having a similar content to yours. This is the most important point of your campaign because all those links incoming from sites with similar theme will reinforce the credibility of your site.

Then you should act on the following three ways: Link exchanging.
Contact the owners asking for a link exchange.

Sign in guestbooks. Many website are inviting visitors to sign in guestbooks. Go there and leave an appropriate comment and do not forget to add the link to your site. Take care what email address you'll provide, as many spammers are scroling guestbooks to collect addresses.

Post in forums or message boards. A lot of webmasters have developed forums and message boards on their site. First read the terms of use. Most of the times you have to sign in and to provide an available email address. Then watch the sense of discussion and post an appropriate comment together with your link. Some forums do not accept links inside of your message but they accept signature files.