source: https://www.bloggingpro.com/archives/2012/03/30/blog-link-building-dos-and-donts/

Definition

Definition: Link building is the process of acquiring incoming links to a page in the interest of increasing the page rank of that page

The value of a link

One way for a search engine to find a website is following links coming from another website.

The links towards pages are valued by the search engine on 2 main criteria: Quality and Quantity

Quality is function of 4 factors:

• Theme/relevance

A link from a website dedicated to book reviews is very relevant if you have an e-bookstore. A link from an insurance company to your bookshop is less relevant. Links from informative, non-commercial websites towards your site, and if they cover a similar subject, are very valuable.

• Link text

The text displayed on top of the hyperlink. This text (should) describe what’s the page you link to is all about. Take care to vary the text on the hyperlink in order to prevent that the search engine considers it spam. (He would consider it spam if the page has only links with each time the same link text)

• Power, authority

Of the site you link from. A site which is well respected and has knowledge authority (e.g. “Wikipedia”) has many incoming and outgoing links. Receiving a link from that type of website is valuable. This is close to “PageRank”. PageRank resembles the mechanism used by scientific/academic publications: how many time are you referred to from other publications.

• Legitimate

Search engines want links which have not been bought. If you buy a link, for example on a directory website covering your business domain, the “nofollow” tag should be on.  This will make this link not counting for he search engine, but not causing any penalty neither.

Quantity

• Although 1 excellent link could value more then 500 average one, quantities do count.

Categorizing link types

• Theme: site which is from a thematic perspective relevant
• Hub: Site acting as hub for a certain subject area or professional domain. Typical for a hub is a large number of incoming and outgoing links.
• Authority: A site which is considered an authority on a certain knowledge domain, subject area. The site has a reputation for providing accurate information. A site with authority can be local (your country, e.g. a book review website) or can be global (e.g.: Wikipedia.org)

Try to collect links from the 4 pie segments for a balanced link profile:

Tricks & Techniques for link building ?

Some tips to get links:

• Linkbait
• ~ Viral marketing
• Twitter, Facebook, Flickr, Youtube,…
• Press releases
• Link in a press announcement (use a suitable link texts!)
• A press release is typically high quality text material
• Blogs
• Use your own network
• Your articles on other websites

Let's explain some concepts of above:
Linkbait is a variation on viral marketing

• Viral marketing is a marketing method trying to using social networks in order to improve the brand-awareness. Consider it mouth to mouth marketing.
• Linkbait is similar, with one difference: the purpose is linkbuilding

Blogs: Leave entries on blogs referring to your website (do it in a subtle way, e.g. joining a discussion on a topic related to your website)

Press releases: If your press release is picked up by journalists, you're a lucky man...: It will likely appear on news sites with a high ranking

Use your own network – e.g. contacts you have in your professional domain

Write quality articles and get them published on websites you don’t own.

References

• Erik-Jan Bulthuis, Nina Baumann, Ramon Eijkemans, Gjalt Jellesma, Arjan Snaterse, handboek SEO resultaatgerichte zoekmachineoptimalisatie, Van Duuren, 2009, Zutphen
• Mark Jansen, Zoekmachine Marketing, Pearson, 2010, Amsterdam