Search Engines need to know the popularity of the website in online to rank them in SERP (Search Engine Results Page). This strategy is used to give the best results (Good Websites) to the (Search Engine Users) users.
Link Popularity is nothing but how popular you are in the internet which can be measured by the number of web sites linked to you. Exactly, Link popularity is a measurement of both the quantity and quality of sites that link to your website. 
As you know quantity of back links is nothing but the number of websites given link to you. Quality explains about the popularity of the websites given link to you. Quality plays vital role than quantity. That is, getting huge number of back links is not a matter. Getting few quality back links will help you to get better visibility in search engines.
Following are the things consider by search engines while counting the link value,
1) Quality
2) Relevancy
3) Quantity
Points to remember while doing links campaign,
- Page having our link should not have more number of outgoing links
- Page having our back link should have more number of incomming links
- Page having our back link should have more number of internal links (transperancy)
- Check the recent cache of that page before getting link from that page.
- Check if any cloaking has been done on that page.
Apart from all the above said points, check the relavancy of the website with yours.
