What are various SEO techniques in details???

I want to perform SEO for websites of my organisation, for which i m working, and want to know various methods, techniques, processes, steps and activities about SEO. I want to know actual actions i have to perform i.e. how can I establish backlinks & raciprocal links? How can PR be increased? How SEO Companies do increase Search Engines Ranking for a website, significantely, in a short span of time??????? etc. etc.