On page SEO factors are important because the search engines rank pages and not web sites. Of course, a web site should be optimised as much as possible throughout all its pages, but each page will be judged on its own merits to a very large degree. Optimising for page SEO factors is the easiest part of overall SEO. It’s the off page factors, getting quality backlinks to the page, that poses the most difficult problem.
If it is the home, or main, page of a web site that you wish to optimise the most, one of the best things you can do to give it a serious boost with the search engines is register a domain that is the exact keyword that the page is optimised for. Having the .com is best, but a .org or .net is pretty much as good too. This can only work for one page on a web site of course, but it is a powerful technique to use.
The first thing you should do for general on page SEO is make the document title in the underlying HTML code the same as the page keyword. You can have additional words in the document title if you wish, but try to place the keyword phrase near the beginning, and keep it fairly short overall.
Your meta tag description is used by many of the search engines in their listings, so use this feature wisely. Use your main keyword in the description near the beginning, and make the description interesting, informative, short and to the point. When a person searching for something come across a listing that has the exact keyword they typed into the search engine in the title, the listing description and in the domain name, they are more likely to click on it that all the others. The search engines will also consider such a page as being highly relevant, and they will rank it accordingly.
The visible part of the page can also be optimised. The page SEO factors that are important here are the main page title and the use of the main keyword in the body of the text, as well as the use of synonyms and related keywords throughout the text. Use an H1 tag to place the page title in. The title should start with the main keyword if possible and can have additional words too.
The body of the text should have the main keyword phrase near the beginning and should then have it included several times more, but not too much. The density of the main keyword phrase should be around 1% to 2% or so. It can be a little higher, but keep it readable. On page SEO factors only need to be there – not overdone.