I would like to know what is the order of on page factors that matter the most with Google search engine?
They're all important. I picked keyword density because when I optimised my keywords on my site even a little bit I then saw a jump up 2 weeks later.
there is no single best method as a proper onpage optimization is combination of all the methods ( i would rather call them steps as the whole onpage optimization is a method itself)
Not sure I could say which is best, I try and make sure I cover all methods to get a full compliment of all factors that effect SEO. The only one I would say does not deserve to be on there at all is Font Style Tags as font style tags should not even be used CSS should be used instead and it makes no different in terms of SEO anyway.
i think title tag,meta description and kws all play a vital role in targeting your website to top in google.