Easiest way to improve sites in google on ON Page seo?
look there are alots of on page thing that needs to be done, you can't say just doing one will take you up.there is no such term like easy in White Hat SEO.
correct kelly burdy there are lots of things to increase ranking so you can do all the seo things.
ways to improve your sites ranking in google are:
Publish relevant content
Update your content regularly
Have a link worthy site.
Use fresh and unique content for website. Set unique and website related keywords.
Remove bad links,choose unique keyword for your website,create your content fresh and relevant,build links from high pagerank sites,apply white hat seo technique.
You can't do that through White Hat SEO.