This means your site must offer something of value to entice other sites to link to yours.
If all your site does is sell products or services, you need to get busy creating some additional linkable content. Examples of linkable content include how-to articles, product reviews, tools, tips and so on. Creating content can be tough, but if you don't have some on your site already, you've got to do it. Adding linkable content not only will encourage others to link to your site, but it will improve the overall quality of your site for your visitors.
Make it easy on yourself by writing about something you know that relates to your site. This column is a perfect example. It teaches without trying to sell something. The best part of creating linkable content is that if you do it well enough, you will find that people will link to your site without you even asking, and that's the easiest way to build links.
You're not a writer? You can always add free tools or free downloads. Also, consider creating a links page prior to requesting a link trade with a site. You can usually expect a better reception from a potential link partner if they can see where you will place the link to their site.