There is not one true one as there is not universal agreement on what SEO actually is and what it involves. This is because people disagree on some of the factors search engines might take into account and no one can settle the argument for sure because the search engines won't (for obvious reasons) make their algorithms public.
However there are some factors (such as original content) that all the major search engines agree on as important.
So the simplest checklist is actually made up of only three points:
The checklist for the first of these can be found on our page Plan your SEO process and this can often be enough to take a site to the top of Google, Yahoo and Bing.
If not you will need to go in search of links, but not any links, and the way to do this is explained on our page Links in SEO
I'm Tim Hill, a Search Engine Optimisation and Online Marketing specialist. I created this site to help others understand that SEO is not a mysterious black art!.
If your a newbie try the Getting Started in SEO page, otherwise feel free to dig around and learn more.