On Page, Off Page optimization both are important all all the time.
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SEO can make the content of your web pages more relevant, more attractive, and more easily read by search engines and their crawling and indexing software.Search Engine Optimization (SEO) is the key tool for the website owners to get more traffic to the website.SEO plays a crucial role in online business websites as well as other interactive sites. With regular update of content on website, SEO helps to get more traffic.
Really all activities is must for seo, But first should be do On page SEO.
after that i prefer some activities like forum posting and blog commenting and other etc.
The easiest way to get traffic to your new website is by the using social networking sites like Facebook, Twitter, and Google+. Share quality posts and information regarding your niche and I am sure it will build trust so people will check your website. Good photos are best as people tend to share photos with their facebook friends.
High quality videos are also a great way especially if the video is helpful to your niche.
Be visible. Be social.. :)
Some SEO techniques that you can take into consideration are-
I know very well build a link is not difficult job but make sure quality link building plays some good role when you plan to reach your destination. So avoid to use un-eathical technique otherwise you should be penalized by the search engine.