It has been said in Google Webmaster Guidelines that any type of links that are created just for the purpose of passing pagerank can be considered as a Spammy Link. Last year it was announced from Google that the practice of link building should be avoided as far as possible. However Google and other search engines still give value to the number of links and anchor text leading to a website.
Natural way of link building is favored by Google to show web pages on search engine results page. For a website the number of backlinks may be losing due to various web spam reporting and Google making the backlink irrelevant. For preventing such scenarios a natural way of link building should be preferred.
Web pages having higher authority ranks high on search engine results page. This is the reason why websites already having page authority shines for articles even when the content on the website is being taken from other blogs. If a website is having low bounce rate and exit rate the content that is published on such website will be having more authority. getting a link from such a website will be considered as good in terms of SEO
The link pointing to a website should be relevant to the content on the website. A website giving away link to an unrelated website is considered as spammy. The context of giving link from a web page should be in such a way that the browsing of the link gives more in depth idea about the content on the web page. The number of links going out of the web page also should not be more than a particular level or else there are chances of getting penalised.
Some website offer reciprocal link exchange which is not a natural way of link building. Websites exchanging links will be having reciprocal links almost equal in number which randomly divert the pagerank of the website. Such practices are not entertained by the Web Spam team at Google.