QUOTE:  Each piece of duplication in your on-page SEO strategy is ***at best*** wasted opportunity. Worse yet, if you are aggressive with aligning your on page heading, your page title, and your internal + external link anchor text the page becomes more likely to get filtered out of the search results (which is quite common in some aggressive spaces). Aaron Wall, 2009

SEO is the practice of optimizing websites to make them reach a high position in Google’s – or another search engine’s – search results. At Yoast, we believe that holistic SEO is the best way to rank your website because you focus on making every aspect of your site awesome. Don’t use any black-hat SEO tricks, because eventually, this will have negative consequences for your rankings. Instead, practice sustainable SEO, with your user in mind, and you will benefit in the long run.
Google, in many instances, would rather send long-tail search traffic, like users using mobile VOICE SEARCH, for instance, to high-quality pages ABOUT a concept/topic that explains relationships and connections between relevant sub-topics FIRST, rather than to only send that traffic to low-quality pages just because they have the exact phrase on the page.
QUOTE: “In place of a pop-up try a full-screen inline ad. It offers the same amount of screen real estate as pop-ups without covering up any content. Fixing the problem depends on the issue you have for example if it’s a pop-up you’ll need to remove all the pop-up ads from your site but if the issue is high ad density on a page you’ll need to reduce the number of ads” Google, 2017
Onsite, consider linking to your other pages by linking to pages within main content text. I usually only do this when it is relevant – often, I’ll link to relevant pages when the keyword is in the title elements of both pages. I don’t go in for auto-generating links at all. Google has penalised sites for using particular auto link plugins, for instance, so I avoid them.
By 2004, search engines had incorporated a wide range of undisclosed factors in their ranking algorithms to reduce the impact of link manipulation. In June 2007, The New York Times' Saul Hansell stated Google ranks sites using more than 200 different signals.[26] The leading search engines, Google, Bing, and Yahoo, do not disclose the algorithms they use to rank pages. Some SEO practitioners have studied different approaches to search engine optimization, and have shared their personal opinions.[27] Patents related to search engines can provide information to better understand search engines.[28] In 2005, Google began personalizing search results for each user. Depending on their history of previous searches, Google crafted results for logged in users.[29]
Additionally, there are many situations where PPC (a component of SEM) makes more sense than SEO. For example, if you are first launching a site and you want immediate visibility, it is a good idea to create a PPC campaign because it takes less time than SEO, but it would be unwise to strictly work with PPC and not even touch search engine optimization.
SEO may generate an adequate return on investment. However, search engines are not paid for organic search traffic, their algorithms change, and there are no guarantees of continued referrals. Due to this lack of guarantees and certainty, a business that relies heavily on search engine traffic can suffer major losses if the search engines stop sending visitors.[61] Search engines can change their algorithms, impacting a website's placement, possibly resulting in a serious loss of traffic. According to Google's CEO, Eric Schmidt, in 2010, Google made over 500 algorithm changes – almost 1.5 per day.[62] It is considered a wise business practice for website operators to liberate themselves from dependence on search engine traffic.[63] In addition to accessibility in terms of web crawlers (addressed above), user web accessibility has become increasingly important for SEO.
Description meta tags are important because Google might use them as snippets for your pages. Note that we say "might" because Google may choose to use a relevant section of your page's visible text if it does a good job of matching up with a user's query. Adding description meta tags to each of your pages is always a good practice in case Google cannot find a good selection of text to use in the snippet. The Webmaster Central Blog has informative posts on improving snippets with better description meta tags18 and better snippets for your users19. We also have a handy Help Center article on how to create good titles and snippets20.
QUOTE: “So there’s three things that you really want to do well if you want to be the world’s best search engine you want to crawl the web comprehensively and deeply you want to index those pages and then you want to rank or serve those pages and return the most relevant ones first….. we basically take PageRank as the primary determinant and the more PageRank you have that is the more people who link to you and the more reputable those people are the more likely it is we’re going to discover your page…. we use page rank as well as over 200 other factors in our rankings to try to say okay maybe this document is really authoritative it has a lot of reputation because it has a lot of PageRank … and that’s kind of the secret sauce trying to figure out a way to combine those 200 different ranking signals in order to find the most relevant document.” Matt Cutts, Google
QUOTE: “The preferred domain is the one that you would liked used to index your site’s pages (sometimes this is referred to as the canonical domain). Links may point to your site using both the www and non-www versions of the URL (for instance, http://www.example.com and http://example.com). The preferred domain is the version that you want used for your site in the search results.” Google, 2018
It is important you spread all that real ‘PageRank’ – or link equity – to your sales keyword / phrase rich sales pages, and as much remains to the rest of the site pages, so Google does not ‘demote’ pages into oblivion –  or ‘supplemental results’ as we old timers knew them back in the day. Again – this is slightly old school – but it gets me by, even today.

You can probably include up to 12 words that will be counted as part of a page title, and consider using your important keywords in the first 8 words. The rest of your page title historically counted as normal text on the page, but recent tests (2019) would indicate this is no longer the case. Words beyond the 12th word may be completely ignored by Google.

I’ve got by, by thinking external links to other sites should probably be on single pages deeper in your site architecture, with the pages receiving all your Google Juice once it’s been “soaked up” by the higher pages in your site structure (the home page, your category pages). This tactic is old school but I still follow it. I don’t need to think you need to worry about that, too much, in 2020.

Many think that Google won’t allow new websites to rank well for competitive terms until the web address “ages” and acquires “trust” in Google – I think this depends on the quality of the incoming links. Sometimes your site will rank high for a while then disappears for months. A “honeymoon period” to give you a taste of Google traffic, perhaps, or a period to better gauge your website quality from an actual user perspective.

Users will occasionally come to a page that doesn't exist on your site, either by following a broken link or typing in the wrong URL. Having a custom 404 page30 that kindly guides users back to a working page on your site can greatly improve a user's experience. Your 404 page should probably have a link back to your root page and could also provide links to popular or related content on your site. You can use Google Search Console to find the sources of URLs causing "not found" errors31.

Some page titles do better with a call to action – a call to action which reflects exactly a searcher’s intent (e.g. to learn something, or buy something, or hire something. THINK CAREFULLY before auto-generating keyword phrase footprints across a site using boiler-plating and article spinning techniques. Remember this is your hook in search engines, if Google chooses to use your page title in its search snippet, and there is a lot of competing pages out there in 2020.
QUOTE: “When our quality algorithms go to your website, and they see that there’s some good content here on this page, but there’s some really bad or kind of low quality content on the bottom part of the page, then we kind of have to make a judgment call on these pages themselves and say, well, some good, some bad. Is this overwhelmingly bad? Is this overwhelmingly good? Where do we draw the line?” John Mueller, Google 2016
Either porn SC or Ads containing porn on non­Porn pages can be very distracting or even upsetting to users. Please refresh the page a few times to see the range of Ads that appear, and use your knowledge of the locale and cultural sensitivities to make your rating. For example, an ad for a model in a revealing bikini is probably acceptable on a site that sells bathing suits. However, an extremely graphic porn ad may warrant a Low (or even Lowest) rating.” Google Search Quality Evaluator Guidelines 2017
The depth of your articles impresses and amazes me. I love all the specific examples and tool recommendations. You discuss the importance of backlinks. How important is it to use a tool to list you on directories (Yext, Moz Local, Synup or JJUMP)? Will Google penalize you for listing on unimportant directories? Is it better to avoid these tools and get backlinks one at a time and avoid all but a few key directories?