Hi Robert, link building is a little more complicated than it used to be after google updates, this link gives you some good info to get started and seomoz is a reliable source.
What is Link Building? Strategies & Examples - The Beginners Guide to SEO

Add me on Skype if you need help.

Hi,
Link building is not difficult. However, it is time consuming. Have you thought about outsourcing your backlink building?

Actually I didn't have enough knowledge about link building.
You can check it. I hope you'll get the perfect answer.

Actually link building is the process of linking back to your site from another site. But since after the algorithm of search engine google has updated, link building without any rule will be valuated much by Google. Check out the page first -

How to Build Links Fast: 101 Tips & Strategies

Look, you must to do quality link building to be ranked by google. You need to link back from the site which has the same keyword for which you are linking back. Here, you have to understand what is the keyword of that site. Finding a word which is your keyword in that site does not mean that it is the keyword of that site. So, be careful always to understand keyword always.

You can build links by these off page techniques.
1.) Directory Submission
2.) Social Bookmarking
3.) Forum Posting
4.) Blog Comments
5.) Article Submission
6.) Press Release
7.) Video Submission.