Link building is considered to be the most important criteria for ranking well in any search engine. Search Engines gives a lot of weight to websites that have quality web pages linking to them. Search Engines consider this to be a vote for that website; normally that’s the index page or home page of the website.
The strategy for making web pages vote for your page is termed as link building strategy in search engine optimization. There are basically two types of links, one is back link and the other is reciprocal link. The difference is simple, in back link a web page votes for the other and in reciprocal link both web pages vote for each other.
With times search engines are realizing the misuse of link building webmasters do to get on top in search engines. Like high page rank web pages started selling back links at a good amount and webmasters started trading reciprocal links.
I think before starting to build links an SEO needs to first understand the product, like when the company is into selling software’s then first try locating the geographical market on internet for it. Let’s elaborate this with an example; a company was into selling online software tools to clients in US. Here the target market was US. So it was very important to have back links that could provide them weight in U.S data centers of the search engines because people searching for these products in US would be connecting to the nearest data center of the search engine and as we all know no 2 data center displays the same results.
The reciprocal link page had PR of 4 so the webmaster was in a decent position of selection before providing a link back.
The criteria’s set were:.
Websites that had their subject related to software industry.

Websites that had their reciprocal link page PR of 3 and above

Website needs to be a US based website

I know some SEO’s would say that with such criteria’s the link building process would be very slow, however, no webmaster would like the search engine to suddenly push their web pages ranking from 1st page to say 10th or so. With the above strategy your website reflects that it recommends only quality website from the same industry that could also be helpful for their visitors.

For quality back link a webmaster can always register their website with highly rated directories, industry specific directories worldwide. The list is something more you try to find more you get.

These factors such as web pages from your region votes for your web page, web pages related to your industry votes for your web page are something no search engines would ever consider spamming, not until they stop giving weight to links from other web pages.
Always remember for a search engine every web page is a unique destination and is identified not only from the title, description, keywords tag, H1, H2, contents but also by how many web pages vote for this page, how many web pages from the same industry vote from them, how many web pages from the same region vote for your web page etc. I could only name these many and always try to fix them where ever I perform my expertise.