are many strategies for the build linking, you can build links with forums signatures, submissions to directories, articles on blogs, social networks, high PR resources etc.
External link building is all about getting inbound links to your website from external websites. Remember that outbound linking is also crucial when it comes to effective link building. That's because the links to the other sites from your own sites matter sometimes.
There are many way of link building. Like directory submission, social bookmarking, article submission, forum posting it depends on you which you prefer
Link building is basically about getting back links for your website through various gray hate techniques. Hope this help!