There are really 2 parts to SEO (Search Engine Optimization), the on page SEO and the off page SEO, which includes SEO backlink building. There are a number of good articles on the web about the topics of off page SEO and SEO backlinks, but they need to be treated with caution. All SEO work, be it on page SEO or off page SEO, is a fluid industry and what is working now may not work tomorrow, and what worked in 2008 (there is a good SEOMoz article written in 2008) very likely doesn't work today. The author of the 2008 SEOMoz article says that, despite talk then, he believed that directory submission was not dead. But, 3-4 years later, it's our experience, and that of many others, that directory submission IS dead, or, at best, more effort than the rewards justify.
Another old, and now fairly fruitless, off page SEO system was writing to thousands of webmasters to beg for reciprocal links. This takes enormous amounts of work with relatively little return. And Google doesn't give the same weight to reciprocal links as it does one way links.
So what is working for off page SEO and SEO backlink building in 2013? It is a little dependant on which search engine you want to optimize for. Yahoo and Bing, while giving weight to off page SEO, give more weight to on page SEO - at least more than Google. They like keyword rich content and the like - so on page SEO. Google, on the other hand, has a very complex algorithm for determining search result relevancy. They are into off page SEO and quality SEO backlink building. And, as the major search engine (estimates are 70-80% of searches), Google is the one we want ourselves and our clients to rank in the most.
When we design a new site, we are thinking about on page SEO as we go, so it's never a case of having to go back and fix it afterwards. As we go, seems the best use of resources to us. However, off page SEO and SEO backlink building can really only start after the new site is launched. We have found from experience that a 6 pronged approach works well for us.
That's how we start, and it also forms the core of our work, but it's by no means all we can do. However, it's a time consuming job whichever way you cut it. And constantly changing.
By far and away, the bulk of our off page SEO effort goes towards SEO backlink building - securing our customers good quality, high PR (Page Rank) backlinks. One of the problems with the old system of writing to thousands of webmasters was that you would invariably end up on irrelevant sites that had low PR = waste of your time, and no real benefit to your site. The way we do it now is less labor intensive, and is much more targeted in terms of avoiding low PR sites. And the results speak for themselves. One recent client we designed a site for had been live on the net with a brand new domain name for a month. Among other terms, we were optimizing for "Sacramento roof repairs". Now the search volume was a little under 300, but the competition was high. He initially ranked #185. After just 3 days on our new system (that's as of today) he ranked #35 - a jump of 145 places!!! And we're only just starting. Now, of course, we can't guarantee that result for everyone, but it proves it does work in the area of SEO backlink building.