Having talked at length about some of the various factors that make up the battlefield of SEO, the last say will always belong to the people who view your content. Building in virality by engaging people on an emotional level and understanding what motivates people at their core is what will generate you the most exposure. People are using the internet as a medium to share knowledge and express feelings about who they are and what defines them. Most decisions we make in life are determined by emotions and less by logic. Any one who can understand this would do very well. The book that I would recommend to help you in understanding the principles that underly this psychology is:
He recounts so many great examples of ideas that were incredibly shareable curiosities that got people talking. This is still going to be the number 1 thing you should be taking on board from this guide. Yes it is very important to have good, quality sharable content, but it would do very little for you without you properly optimising everything first. It goes without saying that SEO in itself is not a business builder, but lays a very good foundation for you to build quality content upon. Good SEO is the grease that keeps the machine moving forward. You will determine what exactly that machine is, a donkey cart, a Rolls Royce or anything else in between.