Not entirely sure I understand your question, but... One version of this is that people go around reading blogs with reasonably high PR. Then they make intelligent comments in the comments section and are permitted to put their url with a link-back... A few things: 1) Don't spam. That will get your comment deleted for sure. 2) See if the blog is NoFollow. If the PR is high, good chance it's a nofollow. Still may be worth doing for the traffic and for the non-google juice.
coz i had read in some forum before they say that the blog networking is not like a link exchange... so this can be done by putting a comment and leave a site link url... thanks!...
Blog Networking is not a link excahnge of any type, blog networking is where you combine and number of blogs together and when you make a post on the main source blog the article is used across the whole network
i have done it before and google has never count those backlinks. i think blog networks are completely useless
blog networking is network of blogs. several blogs, sometimes hundreds under one network. mostly done by people who are selling links or article posts on the entire network. it gets advertised as "your article on 900 unique blogs, get 2700 backlinks" like that. sounds catchy but one thing to remember that most people operating blog networks register hundreds of blogs under only few unique IPs so you don;t really get credit for all those unique links. and another thing to remember that if you post same article on a the entire network, you risk the chance of getting penalized by google for duplicate content. however, small blog networks that are SE optimized and allow you to post unique article or atleast offer article spinning can be helpful