Link building is one of the essentials of search engine optimization.There are several methods of link building which can help your website to become popular on the world wide web. The techniques are mentioned below:-
Directory Submission- This is one of the primary methods of link building which makes use of web directories for listing a website. These are free resources to list your website and get traffic, link as well as pagerank, if the link is do follow.
Forum Posting- This technique makes use of available niche forums where the user can create account and add links on their signature. This signature serves as the sources of Url. The best way is to find niche do follow forums and leave valuable suggestions and advice which adds to the contribution.
Blog commenting- Many people do not use blog commenting as a backlink strategy but this can come handy in all situations. We should keep in mind to add valuable comments on the blog which is helpful for the audience. It is always better to get do follow links but no follow links are not of any harm as it can lead to traffic.
Link Exchange- The method of reciprocal link building has faded away after the Penguin and Panda updates but three way link exchanges still work. Three way link exchanges work in the same way as one way links, as such it is one of the preferred ways of link building.
Web 2.0 links- These include sites such as blogger, facebook, twitter, linkedin, wordpress etc. These links serve as a great resource for building links. Web 2.0 links can be divided into the following parts:-
Social bookmarking- Popular and famous websites are being bookmarked by people from all over the world. These are great resources for getting traffic as well as links. Some popular bookmarking sites include digg,stumbleupon,jumptags,reddit,mister-wong,delicious,folkd,diigo etc.
Social networking- These sites helps to spread the buzz about your company and their products or services. These include Facebook, Twitter, Myspace, Skyrocket, Orkut etc.
Blogging- Some of the biggest platforms of web 2.0 links are blogger and wordpress. You can create free blogs on these sites, add quality content and link your main website from these blogging platforms. Some of the widely popular blogging sites are blogger, wordpress,livejournal,weebly,journalhome, etc.
Article submission- The concept is simple in this way of link building. You need to register yourself on the available article submission sites, create some quality content and adds links from the site to your main website.

Author's Bio: 

Learn Seo from one of the popular Seo blogs – Seo Sandwitch. The site has list of seo tools and a set of seo interview questions and answers .