Google says: "Have relevant sites link to yours". The key word here is 'relevant'.
Submit Your Site
Webmasters: Complete the form below to submit your link request to our site. You will be contacted via email when your site is approved.NOTE: All fields are required.If you already have an active listing on our site, you can click here to edit your current listing. Sites in the "other sites" category must have a Google page rank greater than 0 to get approved.
Select the category your site should be placed in