"Do Follow" to increase your Page Rank

My friend told me about "Do Follow" with blogs. I means he leave comment on other blog and put his url and other people also put comment and url on his blog. Every time another site enjoys your article, there is a chance they will copy and paste it to their own blog, leaving a linkback (or trackback) URL to your page so that the readers know where it came from. In simple sentence I can describe this with "If you put your comment on my blog I will put my comment on your blog too"And guess what, you now have incoming link from another site. Your PR will increase too because when Google index the blog, Google will find your the url of blog too. You can get higher position on Google search. The advantage this tips can be increased your Adsense earning because many people will visit your blogMaybe you think it's so simple, but actually you must change some script on your blog tempalate. Why? Because blog usually put 'nofollow' attribute on comment script. This is done to discourage comment spam. Search engine will not index website that have nofollow attribute on the link script. But you can edit it on customization template of your blog.You can read about how to remove 'nofollow' attribute on your blog hereAfter that you can ask some blogger to join "Do Follow" with your blog and make sure that the blog remove 'nofollow' on comment script. Put your comment and blog url into their blog, and hoping that they forget to add their comment into your blog :)