When I started with Search Engine Optmimization (SEO) in 1992, it was just a few simple steps to promote a website. Mostly external tools added your site to hundreds of search engines and indexes using a descriptions and a few keywords. The years methods grew more and more sophisticated as search engines required more and more parameters to evaluate web sites.
Some companies like to sell backlinks via spam or other questionable means, but people forget for example Googles intend to simply serve the best results for a query. Meaning a proper, standard compliant and fast loading website with up to date content.
Many websites do not focus on optimization at all. This means that you can even through small changes score good ranking results. The further you want to rise to the front page the more consistent these changes need to be. Content Management System, Search Engine Optimization, Website Optimization and Monitoring all need to work hand in hand to provide the best result – your top ranking.