I have been doing SEO for clients for over a decade now. Prior to doing client SEO I had always been a bit of a computer nerd who build my own website back in the late 90’s and started doing SEO then myself. It was the wild west and anything went. But as time went on a clear pattern started to emerge with Google and what they wanted. They want you to get your links from the highest quality sites, site that they trust.
They want your linking to be natural, what they mean by that is natural behavior. Natural behavior to them of course is not necessarily natural behavior to the lay person. As I understood more and more the mindset of the people involved in their search algorithm I found found a surprisingly effective way of ranking sites and doing it in a way that met their criteria.
My experience and constant testing will get you to the first pages that are relevant to your business.