* Through link exchanges with related blogs and sites
* By making useful comments on other websites and blogs so that
click your link to your site
* Posting in related forums and newsgroups
* Via article marketing where you put your link in the resource box
* By posting free resources on your website so that other websites can
link to them

These are just some of the ways. Natural one-way link building is the best since they are the most valuable in terms of high search engine ranking as they measure your website link popularity by counting the number of one-way links coming into it.