Before doing on page for your website you must need to keyword research , once you got the target keyword you just start doing on page optimization for your website . These are the main task which we do for On-page changes : Pre-analysis report Generate for a Website Optimized Title of a site and put targeted keyword into it which is suitable to promote for your website Optimized Description of a website with respect to targeted keyword Optimized Meta keyword for targeted keyword Content Optimization Robots.txt file and Sitemap creation and uploadation Redirection of website URL 404 Error page Internal links of pages and anchor tag optimization Image Optimization Navigation Optimization Make Google Webmaster tool usable for Website and put website into it Put website in Google Analytics to get estimation of traffic and visits on website Sitemap Generation and uploadation These are some of the important task which make your website more SEO friendly .
As in Google individual page is ranking and not a website. So optimize all pages with great on page optimization(I think you can google it for the list of on page factors), and off page optimization. In off page focus on relevant and quality links.