Search Engine Land has posted a cleaver graphical representation of the factors involved in search engine optimization, presented as a mock periodic table of the elements. You can find their original post here.
They categorize SEO ranking factors into groups including On-Page SEO factors (Content, HTML, Architecture) and Off-Page SEO factors (Links, Social, Trust, Personal), and also lay out two negative categories, Violations and Blocking.
Violations include spam techniques like keyword stuffing, hidden text, cloaking and link spam.
Blocking is when someone chooses to exclude your page from their search results. When a user is signed in to Google and clicks a search result but then quickly clicks back to the search results page they are given the option to block that site from future search results. So if they have blocked your site, nothing you do for SEO will get you to appear to that user.
If too many people block your site, Google will take this into consideration and may affect your search engine ranking for all users. To avoid this, make sure your website is well-designed, easy to use, and loads fast. A few people blocking you won’t hurt, but if your site consistently annoys your visitors it could have dramatic impacts on your search traffic.