Before launching into all the different things you can do to improve search engine optimization - i.e. get your website found in top search results - it is worthwhile taking a moment to consider what Google and Bing are looking for. Think about what 'they' want.
You also need to consider what is practical, or even possible, for your brand and website(s). (Remember that thing about the Time, Money and Effort formula to success.)
Search optimization isn't limited to websites anymore, either. You'll see more videos, and social 'stories' showing up in top results.
It's Just Advertising, Baby
Search engines are in the business of SELLING ADVERTISING. They use search features to attract people to look at their website in order to show paid ads.
They compete to have the better 'search product'; and put a lot of effort and resources into generating what they consider to be the 'best' results to search queries.
The Google Artificial Intelligence Search Algorithm (called RankBrain) considers many many different factors ranging from what it knows about the person doing the searching, their current location, and more - and that is before they even start considering whether potential websites offer the best results.
This is a complex process, but it can be boiled down into basic concepts.
In simple terms envision an answer to a question, or a solution to a problem. This Q&A aspect is actually written into the Google search algorithm patents.
Anticipate what your target audience looks for when they use search engines, focus on their 'intent'. This approach to creating content has the potential to boost your search results by better matching searches with your content offer, and will improve your user experience which in turn could also boost your authority and search rankings.
First Things First
The first step in SEO search engine optimization and building 'authority' is to tell the search engines (Google & Bing) what your 'brand' is about, and especially your website.
Data Data Data
Google owns over 1 million computers (yes, really) that spend all day looking at the internet and crunching the numbers. Google looks for 'data relationships' to determine Relevancy and Authority. ie. what's related to this & should it be considered to be correct.