Link building is one of the main step following in search engine optimization.
Two way links are better than three way links.
Most of the them are trying to do three way links,because they don't want to open a link page in their main site.
Instead of that,they will provide you a junk sites. So,Webmaster must be aware of these kind of 3 way links.
And also these type of link exchanges never helps you in lift up your website in search engines. Hence, webmaster can make a two way link exchange with other websites. It will helpful in many ways in developing your website.
Link Building Strategy is one of the main step in off-page optimization.