So far i think, the number of links do not matter but the Quality of links do matter. Ant it's the way what Search Engines want.

So, we focus on Quality of Link Building. It's our Goal.

  

There are three types of Link Building

(1)  Onw way - It's very good for any site.You don't need to give link back.Just Your link will be added.

(2) Reciprocal - It's very popular  way of link exchange.Here u need to give link back on the same domain for which  you are doing link exchage.

(3) Three way - Here you need to give link back but  it is not neccessery to give on the same domain for which  you are doing link exhchange,You can give link back on other sites.

 Good quality link building is crucial to obtain high search engine ranking . Shortcuts like using automated link submissions or link harvester software or linking to low quality unrelated sites can be detrimental to the website