Things that effect SEO the most
I believe that more important than those are the meta elements. That is, the tags and attributes that go behind the scenes on a web page (i.e. inside the HTML code).
The H1, H2, H3 tags, for example, are taken into consideration by search engines to determine the structure of your content, and to filter the most important sections out. Your single post page titles should therefore always be wrapped by H1 tags (as opposed to using the H1 titles on your blog name or logo, as many people do).
Finally, it is also important to make sure that your main content comes as soon as possible on your code. That is, if you have a sidebar and a main content area, structure your design in a way that the main content area loads first, and after that the sidebar, footer and so on.