The fundamentals of link building are, have always been and always will be, based on good quality (i.e., useful, interesting, entertaining, educational) content. Because if there is no good content on your site that people can link to, it will be very difficult to convince them to do so.
Link Development (Link Building)
Link development is one of the most controversial and often talked (written) about topics of the search engine optimization industry. Since backlinks are the most vital component of any search engine optimization campaign, and at the same time the most time consuming and consequently most expensive (assuming they are good quality links and not just random directory submissions and blog comment spam) part, inevitably, there are many service providers who offer inexpensive link building services in order to attract and impress potential clients. Such schemes include large volumes of directory submissions (e.g., 200 directory submissions per month), worthless blog and forum comment spam (e.g., 100 blog links per month), or article writing and submissions which result in extremely poor quality content published on equally low-quality article directories which contribute in no positive way to ranking improvements. So if someone is quoting you a $500 per month search engine optimization services which includes large volumes of directory submissions, blog posts, articles, blog/forum comments and so on, all you will be doing is throwing your money away. This is not to say that you can’t get link-work for $500 per month; however, it won’t be for a large volume of links.
Good quality link development work focuses on quality rather than quantity. A well researched and relevant, good quality link is worth many times more than hundreds of free directory submissions.