Very in-depth information, Brian. I love the part about updating old content, I still find old articles in search results, sometimes 3+ years ago that are clearly out of date when it comes to marketing topics. I usually skip those results, and wonder how that content is still ranking, but it would be great if everyone updated that content. This entire post is full of useful tips, as usual. I am bookmarking now, and sharing-

Search engine spiders can only spider through text. They will use the content on your site to determine what your site is about, which in turn will help to decide how highly your site will be ranked for specific keyword phrases when visitors type them into the search engines. For this reason, keyword research is critical to obtaining natural search engine placement and should be at the top of your list when mapping out your SEO strategy.
When Googlebot crawls a page, it should see the page the same way an average user does15. For optimal rendering and indexing, always allow Googlebot access to the JavaScript, CSS, and image files used by your website. If your site's robots.txt file disallows crawling of these assets, it directly harms how well our algorithms render and index your content. This can result in suboptimal rankings.
Of course, we are always thinking about cost/value/likelihood we can upgrade the best content in the vertical—it is almost always the case that the low competition content, although lower benefit, also doesn’t need the same content quality the high competition terms do, so we can sometimes capture more benefit at a faster velocity by hitting those terms earlier.

Search engine optimization (SEO) is often about making small modifications to parts of your website. When viewed individually, these changes might seem like incremental improvements, but when combined with other optimizations, they could have a noticeable impact on your site's user experience and performance in organic search results. You're likely already familiar with many of the topics in this guide, because they're essential ingredients for any web page, but you may not be making the most out of them.
Early versions of search algorithms relied on webmaster-provided information such as the keyword meta tag or index files in engines like ALIWEB. Meta tags provide a guide to each page's content. Using metadata to index pages was found to be less than reliable, however, because the webmaster's choice of keywords in the meta tag could potentially be an inaccurate representation of the site's actual content. Inaccurate, incomplete, and inconsistent data in meta tags could and did cause pages to rank for irrelevant searches.[10][dubious – discuss] Web content providers also manipulated some attributes within the HTML source of a page in an attempt to rank well in search engines.[11] By 1997, search engine designers recognized that webmasters were making efforts to rank well in their search engine, and that some webmasters were even manipulating their rankings in search results by stuffing pages with excessive or irrelevant keywords. Early search engines, such as Altavista and Infoseek, adjusted their algorithms to prevent webmasters from manipulating rankings.[12]
“In conclusion, this research illuminates how content characteristics shape whether it becomes viral. When attempting to generate word of mouth, marketers often try targeting “influentials,” or opinion leaders (i.e., some small set of special people who, whether through having more social ties or being more persuasive, theoretically have more influence than others). Although this approach is pervasive,recent research has cast doubt on its value (Bakshy et al. 2011; Watts 2007) and suggests that it is far from cost effective. Rather than targeting “special” people, the current research suggests that it may be more beneficial to focus on crafting contagious content. By considering how psychological processes shape social transmission, it is possible to gain deeper insight into collective outcomes, such as what becomes viral.”