How on page and off page optimisation are necessary a web site.

[metajack]

The first thing you should do is on-page optimisation, that includes doing keyword research, writing unique content, titles, and off-page when you start link building

[StoneWilson]

On page, you need to create more original contents, add good tittle and description for them, then build internal link well. Off page, link building, website advertising, make your website more famous.

[shafiqwork]

if you want to increase the visibility of website you can use on page and off page optimization.various steps has been taken in on page and off page optimization.
On page optimization:
Keywords Selection, Title tag, Meta tags, Important HTML tags , Link & Image, Website Content, Url Structure

Off page optimization:
Article Submission, Forum Posting, Directory Submission, Blog Commenting, Press Releases, Social bookmarking