Link building is an important task ignored by most of the seo analysts, yet the relevancy and quality of back links, not just a large number of back links can make you stand the cut throat competition in SERP rankings.
Google’s guidelines must be followed in building quality links to a website. When it comes to building links most seo companies either follows buying, selling links to high page rank sites but in the long run it doesn’t be fruitful to sell or buy links as Google may blacklist them. Google rates back links from sites that are relevant and offer one way link exchange higher than those offering reciprocal link exchanges.Some directories offer one way link exchange though their review period for inclusion in the directory may be longer. Quality sites may get less time in getting listed in free directories like Google, DMOZ etc. Websites that follows Link farming, link baiting, and buying or selling links are not considered by Google to exchange links. Reciprocal link exchange can also be considered but only with those websites that follow guidelines set up by Google and having relevant category. Also, the website must not be indulged in third party link exchanges. Another most important factor that is rated high by Google is the domain age of a website.
Higher the domain age of a website, higher is its trustworthiness. Generally speaking, if a website has a domain age of more than one year, then it is considered as trustworthy in terms of exchanging links.