1. soem webmaster may delete your links to sites after you have have linked back. they just cheat others and in order to make a one-way links rather than two-way links. but it is the most common way and people may find it easily. 2.try to reduce the page link juice or PR value on purpose. it means links pages have useless links to the sites. 3. add nofollow on the links which make the links can mot delieve the linkjuice to your site. these are several tips on this topic, if you have some more tips, please add and introduce to us.