The secret of SEO is actually not a secret at all. That's not to say SEO is a simple task that anyone can easily master. Nor does it imply SEO is not important. It is.
But the secret of SEO is often less about SEO.
The Secret Of SEO
So the secret? Improving the user experience. Yes, making the overall experience of your customer's visit to your site as enjoyable, educational and simple as possible.
So much so, that Google is able to pick up this wonderful experience through metrics. Whether it be time on page, bounce rate, returning visits and more. Please see, Search Terminology for more.
Google likely uses some complexity in their algorithm (likely, because I've never seen it). But that is less about the process of matching searcher with websites and more about filtering out the scammers.
Filtering out those trying to game the system. Sites that deploy tools like buying external links in mass. Low quality, spam links. Or maybe copying content, hijacking a website to refer traffic and more. Black hat SEO if you will.
As I've said before, I think of Google as match.com. They have one goal. Provide a quality service of matching two parties, anywhere in the world, who share a common interest.
In the case of search, matching a searcher with the website that best meets their needs. A website that will best answer their questions.
In providing a match, Google is staking their relationship on the result. Too many bad referrals and that user switches to Bing or Yahoo for example.
So for Google it's about weeding out the spam sites. The sites who provide a lousy customer experience. The ones who may look good in their photo, but have horrible table manners.
Please see How Google Works for more.
So focus on the user experience. Write quality content that is relevant, articulate and answers questions. Please see Great Website Content for more.
Make sure navigation is easy to follow. Photos are optimized to improve page speed. And of course personalize your site to differentiate yourself.
The Secret Of SEO
So getting back to the secret of SEO. Improving crawl errors, adding a site map, indexing with Google and more are important. Very important. But don't forget user experience.
Often more can be achieve through the traffic that results from a great user experience than from optimizing Google's ability to read your site.
If traffic is there, Google needs to find you. Notice I said, has to, not will. They are looking for high quality sites.
SEO can decrease the time it takes to find you. But when found, you need to be worthy in the eyes of Google and your customers. And that is the secret of SEO.